Nature photographers posting to social media help with protecting biodiversity

Nature photographers posting to social media are helping improve biodiversity conservation mapping in South Asia, and the method could go global.

Dr Shawan Chowdhury from UQ's School of the Environment led an international team which scoured images on Facebook nature photography groups in Bangladesh, to add to the existing Global Biodiversity Information Facility database.

"We found 44,000 photos of almost 1,000 animal species, including many birds and insects, 288 of which are considered threatened in Bangladesh," Dr Chowdhury said.

"This has vastly improved habitat mapping across the country where only 4.6 per cent of land is designated as protected.

"We identified many more high-priority areas for conservation, spanning 4,000 square kilometres for birds and 10,000 square kilometres for butterflies.

"We'd been missing out on the distribution data of hundreds of endangered species in Bangladesh so this is a big result.

"This could change the way scientists gather biodiversity information in the future, especially in regions where there is a lack of reliable and up-to-date structured monitoring to inform conservation efforts."

In Australia, social media posts are being used to track pest species.

"A South Asian butterfly, called the tawny coster, entered Australia in 2012," Dr Chowdhury said.

"We've searched for additional locality records from Facebook to analyse the movement, ecology and colonisation status of this species and shown that it expanded at about 135 kilometres per year in Australia between 2012 and 2020."

Co-author Professor Richard Fuller from UQ said while Facebook had been helpful, there are some big opportunities for social media companies.

"There is currently no automated way to collect this information, and it was a very arduous task for us to do it manually." Professor Fuller said.

"We hope our research can inspire the development of technology such as an app that transfers biodiversity data posted on Facebook directly to the global biodiversity databases.

"This way, conservation scientists can easily access that data and use it."

Read more at Science Daily

AI algorithm unblurs the cosmos

The cosmos would look a lot better if Earth's atmosphere wasn't photo bombing it all the time.

Even images obtained by the world's best ground-based telescopes are blurry due to the atmosphere's shifting pockets of air. While seemingly harmless, this blur obscures the shapes of objects in astronomical images, sometimes leading to error-filled physical measurements that are essential for understanding the nature of our universe.

Now researchers at Northwestern University and Tsinghua University in Beijing have unveiled a new strategy to fix this issue. The team adapted a well-known computer-vision algorithm used for sharpening photos and, for the first time, applied it to astronomical images from ground-based telescopes. The researchers also trained the artificial intelligence (AI) algorithm on data simulated to match the Vera C. Rubin Observatory's imaging parameters, so, when the observatory opens next year, the tool will be instantly compatible.

While astrophysicists already use technologies to remove blur, the adapted AI-driven algorithm works faster and produces more realistic images than current technologies. The resulting images are blur-free and truer to life. They also are beautiful -- although that's not the technology's purpose.

"Photography's goal is often to get a pretty, nice-looking image," said Northwestern's Emma Alexander, the study's senior author. "But astronomical images are used for science. By cleaning up images in the right way, we can get more accurate data. The algorithm removes the atmosphere computationally, enabling physicists to obtain better scientific measurements. At the end of the day, the images do look better as well."

The research will be published March 30 in the Monthly Notices of the Royal Astronomical Society.

Alexander is an assistant professor of computer science at Northwestern's McCormick School of Engineering, where she runs the Bio Inspired Vision Lab. She co-led the new study with Tianao Li, an undergraduate in electrical engineering at Tsinghua University and a research intern in Alexander's lab.

When light emanates from distant stars, planets and galaxies, it travels through Earth's atmosphere before it hits our eyes. Not only does our atmosphere block out certain wavelengths of light, it also distorts the light that reaches Earth. Even clear night skies still contain moving air that affects light passing through it. That's why stars twinkle and why the best ground-based telescopes are located at high altitudes where the atmosphere is thinnest.

"It's a bit like looking up from the bottom of a swimming pool," Alexander said. "The water pushes light around and distorts it. The atmosphere is, of course, much less dense, but it's a similar concept."

The blur becomes an issue when astrophysicists analyze images to extract cosmological data. By studying the apparent shapes of galaxies, scientists can detect the gravitational effects of large-scale cosmological structures, which bend light on its way to our planet. This can cause an elliptical galaxy to appear rounder or more stretched than it really is. But atmospheric blur smears the image in a way that warps the galaxy shape. Removing the blur enables scientists to collect accurate shape data.

"Slight differences in shape can tell us about gravity in the universe," Alexander said. "These differences are already difficult to detect. If you look at an image from a ground-based telescope, a shape might be warped. It's hard to know if that's because of a gravitational effect or the atmosphere."

To tackle this challenge, Alexander and Li combined an optimization algorithm with a deep-learning network trained on astronomical images. Among the training images, the team included simulated data that matches the Rubin Observatory's expected imaging parameters. The resulting tool produced images with 38.6% less error compared to classic methods for removing blur and 7.4% less error compared to modern methods.

When the Rubin Observatory officially opens next year, its telescopes will begin a decade-long deep survey across an enormous portion of the night sky. Because the researchers trained the new tool on data specifically designed to simulate Rubin's upcoming images, it will be able to help analyze the survey's highly anticipated data.

For astronomers interested in using the tool, the open-source, user-friendly code and accompanying tutorials are available online.

"Now we pass off this tool, putting it into the hands of astronomy experts," Alexander said. "We think this could be a valuable resource for sky surveys to obtain the most realistic data possible."

Read more at Science Daily

Thousands of native plants are unphotographed, and citizen scientists can help fill the gaps

Scientists have documented plant species for centuries to help us understand and protect the incredible diversity of flora in our world. But according to new research, many have never actually been photographed in their natural habitats -- and that's a problem.

Researchers from UNSW Sydney and the Australian Institute of Botanical Science, part of the Royal Botanic Gardens and Domain Trust, surveyed 33 major online databases of plant photographs to examine the photographic record of Australian plant species. The findings, published in New Phytologist, reveal out of 21,077 native Australian vascular plant species, almost 20 per cent lack a verifiable photograph.

Lead author of the study and UNSW Science PhD student Thomas Mesaglio says Australia is one of the richest areas in the world for native species.

"It was surprising to see how many plant species had just line drawings, illustrations, paintings, or even no media at all," Mr Mesaglio says.

Dr Hervé Sauquet, co-author of the study and Senior Research Scientist at the Australian Institute of Botanical Science, is based at the National Herbarium of New South Wales.

"All species of plants ultimately rely on specimens in herbarium collections for their identification," Dr Sauquet says. "Yet, even in this digital age where most herbarium specimens have been scanned and are accessible on the web, photos of live plants in the wild remain in critical need."

Senior author of the study from UNSW Science Associate Professor Will Cornwell says a lack of detailed photos can have real consequences. Many plant species that are difficult to identify in the wild may go extinct if scientists cannot properly identify them with the help of photos.

"We had assumed every plant species would have simply been photographed by someone, somewhere, throughout history. But it turns out this isn't the case," says A/Prof. Cornwell.

"This is where citizen scientists can come in and help us fill this gap with their photos."

Gaps in the photographic record

Photographs can help botanists and taxonomists who work with plant specimens by preserving characteristics like flower colour that get lost over time in their samples. They can also show additional features, such as the orientation of leaves or bark appearance, and add ecological context.

"Having a comprehensive photographic set helps us to be confident in our identifications," Mr Mesaglio says. "Particularly when it is practically challenging to collect and preserve the entire plant, photos complement the physical voucher by showing the soil type, the habitat it's growing in, and other species growing alongside it."

But it turns out not all plant groups are photographed equally. Just as some animals receive less attention than others, there might also be a bias against less charismatic plants.

The study found the most well-photographed plant groups tend to be shrubs or trees with more noticeable or spectacular features, such as colourful flowers. Banksia, for example, is one of only two Australian plant genera with more than 40 species to have a complete photographic record. Meanwhile, the family with the most significant photo deficit was Poaceae -- commonly known as grasses -- with 343 unphotographed species.

"We noticed a charisma deficit, so the species that tend to be harder to see are the ones missing out," Mr Mesaglio says. "They may have innocuous or pale-looking flowers or be smaller and harder to spot grasses, sedges and herbs."

Geography also affected the photographic record. While most species across the south-eastern states of Australia have comprehensive records, Western Australia had the largest void, with 52 per cent of all unphotographed species found there.

"The primary 'hotspots' for unphotographed Australian plants are areas with high plant diversity, but the environments are rugged and often difficult to access, particularly by road," Mr Mesaglio says. "But it means there's an exciting opportunity to visit these locations because we might capture something that has never before been photographed."

Activating citizen scientist snaps

It's one thing to have comprehensive photographic records for professional scientists to use in identification guides. But when the plant world is under threat from multiple fronts, including habitat clearing and climate change, photos can help engage the public in plant science.

"People can engage with, sympathise with, and get much more excited about plants with photographs, which is vital when our natural environments are more at risk than ever," Mr Mesaglio says.

"Because digital photography is so accessible now, anyone can also help make a meaningful contribution to science using the camera in their pocket."

Using a platform like iNaturalist, keen citizen scientists can have their snaps identified by experts and share the data with aggregators like the Atlas of Living Australia and the Global Biodiversity Information Facility to be used in research and conservation.

"Since April last year, we've identified nearly 10 per cent of those previously unphotographed species thanks to members of the public uploading their photographs and experts who've kindly identified them," Mr Mesaglio says. "There could be many more in personal collections or behind paywalls just waiting to be shared."

The researchers recommend a standardised system for scientific plant photography be developed, starting with a requirement in the International Code of Nomenclature for Plants to include at least one field photograph where possible in new species descriptions. They also suggest all new species descriptions be published as Open Access in searchable databases with Creative Commons licensing to maximise their usage.

"We also suspect more photos exist, but they're hidden away on social media or behind scientific paywalls that aren't accessible, discoverable, or searchable," Mr Mesaglio says.

Read more at Science Daily

Could all your digital photos be stored as DNA?

On Earth right now, there are about 10 trillion gigabytes of digital data, and every day, humans produce emails, photos, tweets, and other digital files that add up to another 2.5 million gigabytes of data. Much of this data is stored in enormous facilities known as exabyte data centers (an exabyte is 1 billion gigabytes), which can be the size of several football fields and cost around $1 billion to build and maintain.

Many scientists believe that an alternative solution lies in the molecule that contains our genetic information: DNA, which evolved to store massive quantities of information at very high density. A coffee mug full of DNA could theoretically store all of the world's data, says Mark Bathe, an MIT professor of biological engineering.

"We need new solutions for storing these massive amounts of data that the world is accumulating, especially the archival data," says Bathe, who is also an associate member of the Broad Institute of MIT and Harvard. "DNA is a thousandfold denser than even flash memory, and another property that's interesting is that once you make the DNA polymer, it doesn't consume any energy. You can write the DNA and then store it forever."

Scientists have already demonstrated that they can encode images and pages of text as DNA. However, an easy way to pick out the desired file from a mixture of many pieces of DNA will also be needed. Bathe and his colleagues have now demonstrated one way to do that, by encapsulating each data file into a 6-micrometer particle of silica, which is labeled with short DNA sequences that reveal the contents.

Using this approach, the researchers demonstrated that they could accurately pull out individual images stored as DNA sequences from a set of 20 images. Given the number of possible labels that could be used, this approach could scale up to 1020 files.

Bathe is the senior author of the study, which appears today in Nature Materials. The lead authors of the paper are MIT senior postdoc James Banal, former MIT research associate Tyson Shepherd, and MIT graduate student Joseph Berleant.

Stable storage

Digital storage systems encode text, photos, or any other kind of information as a series of 0s and 1s. This same information can be encoded in DNA using the four nucleotides that make up the genetic code: A, T, G, and C. For example, G and C could be used to represent 0 while A and T represent 1.

DNA has several other features that make it desirable as a storage medium: It is extremely stable, and it is fairly easy (but expensive) to synthesize and sequence. Also, because of its high density -- each nucleotide, equivalent to up to two bits, is about 1 cubic nanometer -- an exabyte of data stored as DNA could fit in the palm of your hand.

One obstacle to this kind of data storage is the cost of synthesizing such large amounts of DNA. Currently it would cost $1 trillion to write one petabyte of data (1 million gigabytes). To become competitive with magnetic tape, which is often used to store archival data, Bathe estimates that the cost of DNA synthesis would need to drop by about six orders of magnitude. Bathe says he anticipates that will happen within a decade or two, similar to how the cost of storing information on flash drives has dropped dramatically over the past couple of decades.

Aside from the cost, the other major bottleneck in using DNA to store data is the difficulty in picking out the file you want from all the others.

"Assuming that the technologies for writing DNA get to a point where it's cost-effective to write an exabyte or zettabyte of data in DNA, then what? You're going to have a pile of DNA, which is a gazillion files, images or movies and other stuff, and you need to find the one picture or movie you're looking for," Bathe says. "It's like trying to find a needle in a haystack."

Currently, DNA files are conventionally retrieved using PCR (polymerase chain reaction). Each DNA data file includes a sequence that binds to a particular PCR primer. To pull out a specific file, that primer is added to the sample to find and amplify the desired sequence. However, one drawback to this approach is that there can be crosstalk between the primer and off-target DNA sequences, leading unwanted files to be pulled out. Also, the PCR retrieval process requires enzymes and ends up consuming most of the DNA that was in the pool.

"You're kind of burning the haystack to find the needle, because all the other DNA is not getting amplified and you're basically throwing it away," Bathe says.

File retrieval

As an alternative approach, the MIT team developed a new retrieval technique that involves encapsulating each DNA file into a small silica particle. Each capsule is labeled with single-stranded DNA "barcodes" that correspond to the contents of the file. To demonstrate this approach in a cost-effective manner, the researchers encoded 20 different images into pieces of DNA about 3,000 nucleotides long, which is equivalent to about 100 bytes. (They also showed that the capsules could fit DNA files up to a gigabyte in size.)

Each file was labeled with barcodes corresponding to labels such as "cat" or "airplane." When the researchers want to pull out a specific image, they remove a sample of the DNA and add primers that correspond to the labels they're looking for -- for example, "cat," "orange," and "wild" for an image of a tiger, or "cat," "orange," and "domestic" for a housecat.

The primers are labeled with fluorescent or magnetic particles, making it easy to pull out and identify any matches from the sample. This allows the desired file to be removed while leaving the rest of the DNA intact to be put back into storage. Their retrieval process allows Boolean logic statements such as "president AND 18th century" to generate George Washington as a result, similar to what is retrieved with a Google image search.

"At the current state of our proof-of-concept, we're at the 1 kilobyte per second search rate. Our file system's search rate is determined by the data size per capsule, which is currently limited by the prohibitive cost to write even 100 megabytes worth of data on DNA, and the number of sorters we can use in parallel. If DNA synthesis becomes cheap enough, we would be able to maximize the data size we can store per file with our approach," Banal says.

For their barcodes, the researchers used single-stranded DNA sequences from a library of 100,000 sequences, each about 25 nucleotides long, developed by Stephen Elledge, a professor of genetics and medicine at Harvard Medical School. If you put two of these labels on each file, you can uniquely label 1010 (10 billion) different files, and with four labels on each, you can uniquely label 1020 files.

Bathe envisions that this kind of DNA encapsulation could be useful for storing "cold" data, that is, data that is kept in an archive and not accessed very often. His lab is spinning out a startup, Cache DNA, that is now developing technology for long-term storage of DNA, both for DNA data storage in the long-term, and clinical and other preexisting DNA samples in the near-term.

Read more at Science Daily

Uncovering the secrets of some of the world's first color photographs

It is often said that before air travel our skies were bluer yet how, in the 21st century, could we ever know what light and colors were like one hundred years ago? Recently, a group of researchers from EPFL's Audiovisual Communications Laboratory, in the School of Computer and Communication Sciences (IC), had a unique opportunity to try to find out.

Normally hidden treasures locked away in the vaults of a handful of museums, the researchers were offered access to some of the original photographic plates and images of the scientist and inventor Gabriel Lippmann, who won the 1908 Nobel Prize in physics for his method of reproducing colors in photography.

In a paper just published in the Proceedings of the National Academy of Sciences (PNAS) the authors explain that most photographic techniques take just three measurements, for red, green and blue, however they discovered that Lippmann's historical approach typically captured 26 to 64 spectral samples of information in the visible region. His technique, based on the same interference principles that recently enabled gravitational waves to be detected and which is the foundation of holography and much of modern interferometric imaging, has been almost completely forgotten today.

"These are the earliest multi-spectral light measurements on record so we wondered whether it would be possible to accurately recreate the original light of these historical scenes," said Gilles Baechler, one of the paper's authors, "but the way the photographs were constructed was very particular so we were also really interested in whether we could create digital copies and understand how the technique worked."

The researchers found that the multi-spectral images reflected from a Lippmann plate contained distortions, although the reproduced colors looked accurate to the eye. When they examined the full spectrum reflected from a Lippmann plate, and compared it to the original, they measured a number of inconsistencies, many of which have never been documented, even in modern studies.

"We ended up modeling the full process from the multi-spectral image that you capture, all the way to recording it into the photograph. We were able to capture the light reflected back from it and measure how it differed from the original," explained Baechler. So, could the team replicate century old light?

"With the historic plates there are factors in the process that we just cannot know but because we understood how the light differed, we could create an algorithm to get back the original light that was captured. We were able to study invertibility, that is, given a spectrum produced by a Lippmann photograph we know it is possible to undo the distortions and reconstruct the original input spectrum. When we got our hands dirty and made our own plates using the historical process, we were able to verify that the modeling was correct," he continued.

While fully modeling a Nobel-prize-winning imaging technique is of significant interest in its own right, the researchers believe that revisiting Lippmann's photographic technique can inspire new technological developments this century.

Read more at Science Daily

Engineers produce a fisheye lens that's completely flat

 To capture panoramic views in a single shot, photographers typically use fisheye lenses -- ultra-wide-angle lenses made from multiple pieces of curved glass, which distort incoming light to produce wide, bubble-like images. Their spherical, multipiece design makes fisheye lenses inherently bulky and often costly to produce.

Now engineers at MIT and the University of Massachusetts at Lowell have designed a wide-angle lens that is completely flat. It is the first flat fisheye lens to produce crisp, 180-degree panoramic images. The design is a type of "metalens," a wafer-thin material patterned with microscopic features that work together to manipulate light in a specific way.

In this case, the new fisheye lens consists of a single flat, millimeter-thin piece of glass covered on one side with tiny structures that precisely scatter incoming light to produce panoramic images, just as a conventional curved, multielement fisheye lens assembly would. The lens works in the infrared part of the spectrum, but the researchers say it could be modified to capture images using visible light as well.

The new design could potentially be adapted for a range of applications, with thin, ultra-wide-angle lenses built directly into smartphones and laptops, rather than physically attached as bulky add-ons. The low-profile lenses might also be integrated into medical imaging devices such as endoscopes, as well as in virtual reality glasses, wearable electronics, and other computer vision devices.

"This design comes as somewhat of a surprise, because some have thought it would be impossible to make a metalens with an ultra-wide-field view," says Juejun Hu, associate professor in MIT's Department of Materials Science and Engineering. "The fact that this can actually realize fisheye images is completely outside expectation.

This isn't just light-bending -- it's mind-bending."

Hu and his colleagues have published their results in the journal Nano Letters. Hu's MIT coauthors are Mikhail Shalaginov, Fan Yang, Peter Su, Dominika Lyzwa, Anuradha Agarwal, and Tian Gu, along with Sensong An and Hualiang Zhang of UMass Lowell.

Design on the back side

Metalenses, while still largely at an experimental stage, have the potential to significantly reshape the field of optics. Previously, scientists have designed metalenses that produce high-resolution and relatively wide-angle images of up to 60 degrees. To expand the field of view further would traditionally require additional optical components to correct for aberrations, or blurriness -- a workaround that would add bulk to a metalens design.

Hu and his colleagues instead came up with a simple design that does not require additional components and keeps a minimum element count. Their new metalens is a single transparent piece made from calcium fluoride with a thin film of lead telluride deposited on one side. The team then used lithographic techniques to carve a pattern of optical structures into the film.

Each structure, or "meta-atom," as the team refers to them, is shaped into one of several nanoscale geometries, such as a rectangular or a bone-shaped configuration, that refracts light in a specific way. For instance, light may take longer to scatter, or propagate off one shape versus another -- a phenomenon known as phase delay.

In conventional fisheye lenses, the curvature of the glass naturally creates a distribution of phase delays that ultimately produces a panoramic image. The team determined the corresponding pattern of meta-atoms and carved this pattern into the back side of the flat glass.

'We've designed the back side structures in such a way that each part can produce a perfect focus," Hu says.

On the front side, the team placed an optical aperture, or opening for light.

"When light comes in through this aperture, it will refract at the first surface of the glass, and then will get angularly dispersed," Shalaginov explains. "The light will then hit different parts of the backside, from different and yet continuous angles. As long as you design the back side properly, you can be sure to achieve high-quality imaging across the entire panoramic view."

Across the panorama

In one demonstration, the new lens is tuned to operate in the mid-infrared region of the spectrum. The team used the imaging setup equipped with the metalens to snap pictures of a striped target. They then compared the quality of pictures taken at various angles across the scene, and found the new lens produced images of the stripes that were crisp and clear, even at the edges of the camera's view, spanning nearly 180 degrees.

"It shows we can achieve perfect imaging performance across almost the whole 180-degree view, using our methods," Gu says.

In another study, the team designed the metalens to operate at a near-infrared wavelength using amorphous silicon nanoposts as the meta-atoms. They plugged the metalens into a simulation used to test imaging instruments. Next, they fed the simulation a scene of Paris, composed of black and white images stitched together to make a panoramic view. They then ran the simulation to see what kind of image the new lens would produce.

"The key question was, does the lens cover the entire field of view? And we see that it captures everything across the panorama," Gu says. "You can see buildings and people, and the resolution is very good, regardless of whether you're looking at the center or the edges."

The team says the new lens can be adapted to other wavelengths of light. To make a similar flat fisheye lens for visible light, for instance, Hu says the optical features may have to be made smaller than they are now, to better refract that particular range of wavelengths. The lens material would also have to change. But the general architecture that the team has designed would remain the same.

The researchers are exploring applications for their new lens, not just as compact fisheye cameras, but also as panoramic projectors, as well as depth sensors built directly into smartphones, laptops, and wearable devices.

Read more at Science Daily

Tool transforms world landmark photos into 4D experiences

 Using publicly available tourist photos of world landmarks such as the Trevi Fountain in Rome or Top of the Rock in New York City, Cornell University researchers have developed a method to create maneuverable 3D images that show changes in appearance over time.

The method, which employs deep learning to ingest and synthesize tens of thousands of mostly untagged and undated photos, solves a problem that has eluded experts in computer vision for six decades.

"It's a new way of modeling scenes that not only allows you to move your head and see, say, the fountain from different viewpoints, but also gives you controls for changing the time," said Noah Snavely, associate professor of computer science at Cornell Tech and senior author of "Crowdsampling the Plenoptic Function," presented at the European Conference on Computer Vision, held virtually Aug. 23-28.

"If you really went to the Trevi Fountain on your vacation, the way it would look would depend on what time you went -- at night, it would be lit up by floodlights from the bottom. In the afternoon, it would be sunlit, unless you went on a cloudy day," Snavely said. "We learned the whole range of appearances, based on time of day and weather, from these unorganized photo collections, such that you can explore the whole range and simultaneously move around the scene."

Representing a place in a photorealistic way is challenging for traditional computer vision, partly because of the sheer number of textures to be reproduced. "The real world is so diverse in its appearance and has different kinds of materials -- shiny things, water, thin structures," Snavely said.

Another problem is the inconsistency of the available data. Describing how something looks from every possible viewpoint in space and time -- known as the plenoptic function -- would be a manageable task with hundreds of webcams affixed around a scene, recording data day and night. But since this isn't practical, the researchers had to develop a way to compensate.

"There may not be a photo taken at 4 p.m. from this exact viewpoint in the data set. So we have to learn from a photo taken at 9 p.m. at one location, and a photo taken at 4:03 from another location," Snavely said. "And we don't know the granularity of when these photos were taken. But using deep learning allows us to infer what the scene would have looked like at any given time and place."

The researchers introduced a new scene representation called Deep Multiplane Images to interpolate appearance in four dimensions -- 3D, plus changes over time. Their method is inspired in part on a classic animation technique developed by the Walt Disney Company in the 1930s, which uses layers of transparencies to create a 3D effect without redrawing every aspect of a scene.

"We use the same idea invented for creating 3D effects in 2D animation to create 3D effects in real-world scenes, to create this deep multilayer image by fitting it to all these disparate measurements from the tourists' photos," Snavely said. "It's interesting that it kind of stems from this very old, classic technique used in animation."

In the study, they showed that this model could be trained to create a scene using around 50,000 publicly available images found on sites such as Flickr and Instagram. The method has implications for computer vision research, as well as virtual tourism -- particularly useful at a time when few can travel in person.

"You can get the sense of really being there," Snavely said. "It works surprisingly well for a range of scenes."

First author of the paper is Cornell Tech doctoral student Zhengqi Li. Abe Davis, assistant professor of computer science in the Faculty of Computing and Information Science, and Cornell Tech doctoral student Wenqi Xian also contributed.

Read more at Science Daily

The secrets behind a creepy photographic technique

In the 1960s, a French artist named Jean-Pierre Sudre began experimenting with an obscure 19th-century photographic process, creating dramatic black-and-white photographs with ethereal veiling effects. Sudre christened the process "mordanҫage," the French word for "etching." Since then, other photographers have used and refined mordanҫage to create unique works of art. Now, researchers reporting in the ACS journal Analytical Chemistry have unveiled the mysterious chemistry behind the process.

In mordanҫage, a fully developed black-and-white photograph is immersed in a solution containing copper (II) chloride, hydrogen peroxide and acetic acid. The solution bleaches the photo to a pale yellow color and partially lifts formerly black areas of the print away from the paper backing. Then, the photographer rinses off the mordanҫage solution and redevelops the print to restore the black color. When the photo is dried and pressed flat, black areas that had lifted from the paper form the veils. Caroline Fudala and Rebecca Jones wanted to better understand the chemical details of this process.

The researchers methodically studied the technique and determined that the hydrogen peroxide and acetic acid soften the photographic paper. This allows copper (II) chloride to permeate the paper and oxidize the metallic silver -- which colors the dark areas of the print -- to silver chloride. The softened surface layers lift off as veils. Then, during redevelopment, the veils darken when silver chloride is reduced back to metallic silver. Et voilà, a spooky photo that's just right for a scary holiday...

From Science Daily

Two fraudsters, one passport

Computers are more accurate than humans at detecting digitally manipulated ID photos, which merge the images of two people, new research has found.

Face morphing is a method used by fraudsters in which two separate identity photographs are digitally merged to create a single image that sufficiently resembles both people. This image is then submitted as part of the application for a genuine passport or driving licence, and if accepted, potentially allows both people to use the same genuine identification document without arousing suspicion.

A new study by psychologists at the University of Lincoln asked participants in one experiment to decide whether an image showed the person standing in front of them. In this task, participants accepted the digitally created morphs around half of the time, while a basic computer model could correctly identify morphs over two thirds of time.

The research used high quality 'face morphs' over a series of four experiments which included screen-based image comparison tasks alongside a live task, designed to mimic a real-life border-control situation in which an agent would have to accept or reject a passport image based on its resemblance to the person in front of them.

Results showed that participants not only failed to spot 51 percent of these fraudulent images, but once they were provided with more information on face-morphing attacks, detection rates only rose to 64 percent. In another experiment, the researchers showed that training did not help participants to detect morphs presented onscreen, and detection rates remained around chance level. The results suggest that the morphs were accepted as legitimate ID photos often enough that they may be feasible as tools for committing fraud, especially in border control situations where the final acceptance decision is often made by a human operator.

When similar images were put through a simple computer algorithm trained to differentiate between morphs and normal photos, 68 percent of the images were correctly identified as morph images, showing the programme to be significantly more accurate than human participants. The algorithm used was relatively basic as a demonstration, and recent software being developed by computer scientists is far more sophisticated and shows even greater levels of success.

Lead researcher Dr Robin Kramer from the University of Lincoln's School of Psychology said: "The advancements and availability of high quality image editing software has made these kinds of 'face morphing attacks' more sophisticated and the images harder to detect.

"Our results show that morph detection is highly error-prone and the level at which these images were accepted represents a significant concern for security agencies. Training did not provide a useful solution to this problem.

Read more at Science Daily

New lens manufacturing technique

Researchers from Washington State University and Ohio State University have developed a low-cost, easy way to make custom lenses that could help manufacturers avoid the expensive molds required for optical manufacturing.

Led by Lei Li, assistant professor in the School of Mechanical and Materials Engineering, and graduate student, Mojtaba Falahati, the researchers developed a liquid mold from droplets that they can manipulate with magnets to create lenses in a variety of shapes and sizes. Their work is featured on the cover of the journal, Applied Physics Letters.

High-quality lenses are increasingly used in everything from cameras, to self-driving cars, and virtually all robotics, but the traditional molding and casting processes used in their manufacturing require sophisticated and expensive metal molds. So, manufacturers are mostly limited to mass producing one kind of lens.

"The molds are precisely finished and are difficult to make," said Li. "It isn't worthwhile to make a mold for low-volume production."

The researchers ran into the problem firsthand as they searched for lenses for their work to develop a portable laboratory reader on a phone.

They first tried to make their own lenses using 3D printing but found it difficult to control the lens shape. They then came up with the idea of using magnets and the surface tension of liquids to literally create free-flowing molds.

They placed tiny, magnetic iron particles into liquid droplets and built a device to surround the droplets with magnets. They then poured the plastic material used in lenses over the droplet. As they applied a magnetic field, the droplet took on a conical lens shape -- creating a mold for the plastic lens material. Once they cured the plastic, it hardened and had the same optical properties and imaging quality as a commercially purchased lens. The liquid droplet remains separate and can be re-used.

The magnets can be moved to change the magnetic field, the shape of the mold, and the resulting lens. The researchers also used bigger or smaller droplets to create lenses of varying sizes.

"We brought the concept of interfacial tension to the field of optics by introducing an innovative controllable liquid mold," said Li. "This novel process allowed us to regulate the shape of a magnetic drop and to create lenses without having to fabricate expensive molds."

From Science Daily

World's fastest camera freezes time at 10 trillion frames per second

The trillion-frame-per-second compressed ultrafast photography system.

What happens when a new technology is so precise that it operates on a scale beyond our characterization capabilities? For example, the lasers used at INRS produce ultrashort pulses in the femtosecond range (10-15 s) that are far too short to visualize. Although some measurements are possible, nothing beats a clear image, says INRS professor and ultrafast imaging specialist Jinyang Liang. He and his colleagues, led by Caltech's Lihong Wang, have developed what they call T-CUP: the world's fastest camera, capable of capturing ten trillion (1013) frames per second. This new camera literally makes it possible to freeze time to see phenomena -- and even light! -- in extremely slow motion.

In recent years, the junction between innovations in non-linear optics and imaging has opened the door for new and highly efficient methods for microscopic analysis of dynamic phenomena in biology and physics. But to harness the potential of these methods, there needs to be a way to record images in real time at a very short temporal resolution -- in a single exposure.

Using current imaging techniques, measurements taken with ultrashort laser pulses must be repeated many times, which is appropriate for some types of inert samples, but impossible for other more fragile ones. For example, laser-engraved glass can tolerate only a single laser pulse, leaving less than a picosecond to capture the results. In such a case, the imaging technique must be able to capture the entire process in real time.

Compressed ultrafast photography (CUP) was a good starting point them. At 100 billion frames per second, this method approached, but did not meet, the specifications required to integrate femtosecond lasers. To improve on the concept, the new T-CUP system was developed based on a femtosecond streak camera that also incorporates a data acquisition type used in applications such as tomography.

"We knew that by using only a femtosecond streak camera, the image quality would be limited," says Professor Lihong Wang, the Bren Professor of Medial Engineering and Electrical Engineering at Caltech and the Director of Caltech Optical Imaging Laboratory (COIL). "So to improve this, we added another camera that acquires a static image. Combined with the image acquired by the femtosecond streak camera, we can use what is called a Radon transformation to obtain high-quality images while recording ten trillion frames per second."

Setting the world record for real-time imaging speed, T-CUP can power a new generation of microscopes for biomedical, materials science, and other applications. This camera represents a fundamental shift, making it possible to analyze interactions between light and matter at an unparalleled temporal resolution.

The first time it was used, the ultrafast camera broke new ground by capturing the temporal focusing of a single femtosecond laser pulse in real time. This process was recorded in 25 frames taken at an interval of 400 femtoseconds and detailed the light pulse's shape, intensity, and angle of inclination.

Read more at Science Daily

Uncovering lost images from the 19th century

A 19th-century daguerreotype image shows the faintest outline of a woman, until the image is recovered through a novel process, developed at Western University and Canadian Light Source Inc, that mapped its mercury content.

Art curators will be able to recover images on daguerreotypes, the earliest form of photography that used silver plates, after a team of scientists led by Western University learned how to use light to see through degradation that has occurred over time.

Research published today in Scientific Reports -- Nature includes two images from the National Gallery of Canada's photography research unit that show photographs that were taken, perhaps as early as 1850, but were no longer visible because of tarnish and other damage. The retrieved images, one of a woman and the other of a man, were beyond recognition.

"It's somewhat haunting because they are anonymous and yet it is striking at the same time," said Madalena Kozachuk, a PhD student in Western's Department of Chemistry and lead author of the scientific paper.

"The image is totally unexpected because you don't see it on the plate at all. It's hidden behind time," continues Kozachuk. "But then we see it and we can see such fine details: the eyes, the folds of the clothing, the detailed embroidered patterns of the table cloth."

The identities of the woman and the man are not known. It's possible that the plates were produced in the United States, but they could be from Europe.

For the past three years, Kozachuk and an interdisciplinary team of scientists have been exploring how to use synchrotron technology to learn more about chemical changes that damage daguerreotypes.

Invented in 1839, daguerreotype images were created using a highly polished silver-coated copper plate that was sensitive to light when exposed to an iodine vapour. Subjects had to pose without moving for two to three minutes for the image to imprint on the plate, which was then developed as a photograph using a mercury vapour that was heated.

Kozachuk conducts much of her research at the Canadian Light Source (CLS) and previously published results in scientific journals in 2017 and earlier this year. In those articles, the team members identified the chemical composition of the tarnish and how it changed from one point to another on a daguerreotype.

"We compared degradation that looked like corrosion versus a cloudiness from the residue from products used during the rinsing of the photographs during production versus degradation from the cover glass. When you look at these degraded photographs, you don't see one type of degradation," said Ian Coulthard, a senior scientist at the CLS and one of Kozachuk's co-supervisors. He is also a co- author on the research papers.

This preliminary research at the CLS led to today's paper and the images Kozachuk collected at the Cornell High Energy Synchrotron Source where she was able to analyze the daguerreotypes in their entirety.

Kozachuk used rapid-scanning micro-X-ray fluorescence imaging to analyze the plates, which are about 7.5 cm wide, and identified where mercury was distributed on the plates. With an X-ray beam as small as 10x10 microns (a human scalp hair averages 75 microns across) and at an energy most sensitive to mercury absorption, the scan of each daguerreotype took about eight hours.

"Mercury is the major element that contributes to the imagery captured in these photographs. Even though the surface is tarnished, those image particles remain intact. By looking at the mercury, we can retrieve the image in great detail," said Tsun-Kong (T.K.) Sham, Canada Research Chair in Materials and Synchrotron Radiation at Western University. He also is a co-author of the research and Kozachuk's supervisor.

This research will contribute to improving how daguerreotype images are recovered when cleaning is possible and will provide a way to seeing what's below the tarnish if cleaning is not possible.

The prospect of improved conservation methods intrigues John P. McElhone, recently retired as the chief of Conservation and Technical Research branch at the Canadian Photography Institute of National Gallery of Canada. He provided the daguerreotypes from the Institute's research collection.

"There are a lot of interesting questions that at this stage of our knowledge can only be answered by a sophisticated scientific approach," said McElhone, another of the co-authors of today's paper. "A conservator's first step is to have a full and complete understanding of what the material is and how it is assembled on a microscopic and even nanoscale level. We want to find out how the chemicals are arranged on the surface and that understanding gives us access to theories about how degradation happens and how that degradation can possibly or possibly not be reversed."

As the first commercialized photographic process, the daguerreotype is thought to be the first "true" visual representation of history. Unlike painters who could use "poetic licence" in their work, the daguerreotype reflected precisely what was photographed.

Thousands and perhaps millions of daguerreotypes were created over 20 years in the 19th century before the process was replaced. The Canadian Photography Institute collection numbers more than 2,700, not including the daguerreotypes in the institute's research collection.

Read more at Science Daily

Ultra-thin camera creates images without lenses

At Caltech, engineers have developed a new camera design that replaces the lenses with an ultra-thin optical phased array (OPA).

Traditional cameras -- even those on the thinnest of cell phones -- cannot be truly flat due to their optics: lenses that require a certain shape and size in order to function. At Caltech, engineers have developed a new camera design that replaces the lenses with an ultra-thin optical phased array (OPA). The OPA does computationally what lenses do using large pieces of glass: it manipulates incoming light to capture an image.

Lenses have a curve that bends the path of incoming light and focuses it onto a piece of film or, in the case of digital cameras, an image sensor. The OPA has a large array of light receivers, each of which can individually add a tightly controlled time delay (or phase shift) to the light it receives, enabling the camera to selectively look in different directions and focus on different things.

"Here, like most other things in life, timing is everything. With our new system, you can selectively look in a desired direction and at a very small part of the picture in front of you at any given time, by controlling the timing with femto-second -- quadrillionth of a second -- precision," says Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering in the Division of Engineering and Applied Science at Caltech, and the principal investigator of a paper describing the new camera. The paper was presented at the Optical Society of America's (OSA) Conference on Lasers and Electro-Optics (CLEO) and published online by the OSA in the OSA Technical Digest in March 2017.

"We've created a single thin layer of integrated silicon photonics that emulates the lens and sensor of a digital camera, reducing the thickness and cost of digital cameras. It can mimic a regular lens, but can switch from a fish-eye to a telephoto lens instantaneously -- with just a simple adjustment in the way the array receives light," Hajimiri says.

Phased arrays, which are used in wireless communication and radar, are collections of individual transmitters, all sending out the same signal as waves. These waves interfere with each other constructively and destructively, amplifying the signal in one direction while canceling it out elsewhere. Thus, an array can create a tightly focused beam of signal, which can be steered in different directions by staggering the timing of transmissions made at various points across the array.

A similar principle is used in reverse in an optical phased array receiver, which is the basis for the new camera. Light waves that are received by each element across the array cancel each other from all directions, except for one. In that direction, the waves amplify each other to create a focused "gaze" that can be electronically controlled.

"What the camera does is similar to looking through a thin straw and scanning it across the field of view. We can form an image at an incredibly fast speed by manipulating the light instead of moving a mechanical object," says graduate student Reza Fatemi (MS '16), lead author of the OSA paper.

Last year, Hajimiri's team rolled out a one-dimensional version of the camera that was capable of detecting images in a line, such that it acted like a lensless barcode reader but with no mechanically moving parts. This year's advance was to build the first two-dimensional array capable of creating a full image. This first 2D lensless camera has an array composed of just 64 light receivers in an 8 by 8 grid. The resulting image has low resolution. But this system represents a proof of concept for a fundamental rethinking of camera technology, Hajimiri and his colleagues say.

"The applications are endless," says graduate student Behrooz Abiri (MS '12), coauthor of the OSA paper. "Even in today's smartphones, the camera is the component that limits how thin your phone can get. Once scaled up, this technology can make lenses and thick cameras obsolete. It may even have implications for astronomy by enabling ultra-light, ultra-thin enormous flat telescopes on the ground or in space."

Read more at Science Daily

From blue and black dresses to turbine blades, here's the science of 'fake fake' photographs

Pictured is the Blade in situ, viewed from below.

Whether it's a blue and black dress -- or white and gold depending on your take -- or a pair of legs streaked with white paint, eagle-eyed viewers are always keen to debate a visual illusion when these puzzling images appear online.

A new study published today reveals the science behind another 'trick of the light' that made high-profile photographs of a major piece of public art appear 'faked' to some people despite the pictures being entirely genuine.

Vision science researchers from the University of Lincoln examined photographs of the art installation, Blade, which took pride of place in the centre of Hull earlier this year. Their interest was triggered when some pictures published online of the work -- a 75-metre long, 25-tonne wind turbine blade -- made the object appear to be super-imposed.

The researchers found that this visual illusion was caused by the particular way light reflected from the blade, which then played on pre-conceived notions people have of how objects are lit in natural settings, effectively altering the object's shape to the human eye.

Daylight hitting the object from above produced shading which created the illusion that the blade was cylindrical, and was being lit from the side rather than above. This subtly reinforced the visual impression that the blade was out-of-place, and that the image of the blade and its backdrop must therefore be a composite of two different scenes.

To demonstrate this, researchers created virtual versions of a cylindrical C-shaped profile and a more complex S-shaped profile, and produced two images of each shape, one lit from above and the other lit from the front. The images demonstrated that the S-shape when lit from above and the C-shape when lit from the front both appeared cylindrical.

Professor of Vision Science, George Mather, from the University of Lincoln's School of Psychology, said: "I saw pictures of the installation in the media, and at first sight the photographs seemed to be clumsy fakes. Something else seemed to be at work too, at least to my eyes as a vision scientist.

"The blade appeared to be a cylindrical object, strangely out-of-keeping with the local environment, lit differently, as though it was superimposed on the scene digitally, but it really was there.

"We had an idea about what it was that conveyed this impression -- light and shadow on the blade which is apparently inconsistent with the surroundings. The computer generated images were a way of testing the idea."

The blade was made by turbine manufacturer Siemens and placed in Victoria Square as a major public art installation to mark the start of Hull's year as the UK City of Culture 2017. Artist Nayan Kulkarni created the installation for Look Up, a programme of temporary artworks designed for Hull's public spaces and places. It used one of the first B75 rotor blades manufactured in Hull.

Read more at Science Daily

The world's fastest film camera: When light practically stands still

The new camera was developed for filming chemistry and physics occurring at extreme speeds.

Forget high-speed cameras capturing 100,000 images per second. A research group at Lund University in Sweden has developed a camera that can film at a rate equivalent to five trillion images per second, or events as short as 0.2 trillionths of a second. This is faster than has previously been possible.

The new super-fast film camera will therefore be able to capture incredibly rapid processes in chemistry, physics, biology and biomedicine, that so far have not been caught on film.

To illustrate the technology, the researchers have successfully filmed how light -- a collection of photons -- travels a distance corresponding to the thickness of a paper. In reality, it only takes a picosecond, but on film the process has been slowed down by a trillion times.

Currently, high-speed cameras capture images one by one in a sequence. The new technology is based on an innovative algorithm, and instead captures several coded images in one picture. It then sorts them into a video sequence afterwards.

In short, the method involves exposing what you are filming (for example a chemical reaction) to light in the form of laser flashes where each light pulse is given a unique code. The object reflects the light flashes which merge into the single photograph. They are subsequently separated using an encryption key.

The film camera is initially intended to be used by researchers who literally want to gain better insight into many of the extremely rapid processes that occur in nature. Many take place on a picosecond and femtosecond scale, which is unbelievably fast -- the number of femtoseconds in one second is significantly larger than the number of seconds in a person's life-time.

"This does not apply to all processes in nature, but quite a few, for example, explosions, plasma flashes, turbulent combustion, brain activity in animals and chemical reactions. We are now able to film such extremely short processes," says Elias Kristensson. "In the long term, the technology can also be used by industry and others."

For the researchers themselves, however, the greatest benefit of this technology is not that they set a new speed record, but that they are now able to film how specific substances change in the same process.

"Today, the only way to visualise such rapid events is to photograph still images of the process. You then have to attempt to repeat identical experiments to provide several still images which can later be edited into a movie. The problem with this approach is that it is highly unlikely that a process will be identical if you repeat the experiment," he says.

Most days, Elias Kristensson and Andreas Ehn conduct research on combustion -- an area which is known to be difficult and complicated to study. The ultimate purpose of this basic research is to make next-generation car engines, gas turbines and boilers cleaner and more fuel-efficient. Combustion is controlled by a number of ultra-fast processes at the molecular level, which can now be captured on film.

For example, the researchers will study the chemistry of plasma discharges, the lifetime of quantum states in combustion environments and in biological tissue, as well as how chemical reactions are initiated. In the autumn, there will be more film material available.

Read more at Science Daily

Ultrafast Camera Captures 'Sonic Booms' of Light for First Time

Just as aircraft flying at supersonic speeds create cone-shaped sonic booms, pulses of light can leave behind cone-shaped wakes of light. Now, a superfast camera has captured the first-ever video of these events.

The new technology used to make this discovery could one day allow scientists to help watch neurons fire and image live activity in the brain, researchers say.

When an object moves through air, it propels the air in front of it away, creating pressure waves that move at the speed of sound in all directions. If the object is moving at speeds equal to or greater than sound, it outruns those pressure waves. As a result, the pressure waves from these speeding objects pile up on top of each other to create shock waves known as sonic booms, which are akin to claps of thunder.

Sonic booms are confined to conical regions known as "Mach cones" that extend primarily to the rear of supersonic objects. Similar events include the V-shaped bow waves that a boat can generate when traveling faster than the waves it pushes out of its way move across the water.

Previous research suggested that light can generate conical wakes similar to sonic booms. Now, for the first time, scientists have imaged these elusive "photonic Mach cones."

Light travels at a speed of about 186,000 miles per second (300,000 kilometers per second) when moving through vacuum. According to Einstein's theory of relativity, nothing can travel faster than the speed of light in a vacuum. However, light can travel more slowly than its top speed — for instance, light moves through glass at speeds of about 60 percent of its maximum. Indeed, prior experiments have slowed light down more than a million-fold.

The fact that light can travel faster in one material than in another helped scientists to generate photonic Mach cones. First,study lead author Jinyang Liang, an optical engineer at Washington University in St. Louis, and his colleagues designed a narrow tunnel filled with dry ice fog. This tunnel was sandwiched between plates made of a mixture of silicone rubber and aluminum oxide powder.

Then, the researchers fired pulses of green laser light — each lasting only 7 picoseconds (trillionths of a second) — down the tunnel. These pulses could scatter off the specks of dry ice within the tunnel, generating light waves that could enter the surrounding plates.

The green light that the scientists used traveled faster inside the tunnel than it did in the plates. As such, as a laser pulse moved down the tunnel, it left a cone of slower-moving overlapping light waves behind it within the plates.

To capture video of these elusive light-scattering events, the researchers developed a "streak camera" that could capture images at speeds of 100 billion frames per second in a single exposure. This new camera captured three different views of the phenomenon: one that acquired a direct image of the scene, and two that recorded temporal information of the events so that the scientists could reconstruct what happened frame by frame.

Essentially, they "put different bar codes on each individual image, so that even if during the data acquisition they are all mixed together, we can sort them out," Liang said in an interview.

There are other imaging systems that can capture ultrafast events, but these systems usually need to record hundreds or thousands of exposures of such phenomena before they can see them. In contrast, the new system can record ultrafast events with just a single exposure.

Read more at Discovery News

Physicists develop a more sensitive microscope

Stanford graduate student Brannon Klopfer helped develop the multi-pass microscope described in the current edition of Nature Communications.

Anyone who has taken a photo in a poorly lit restaurant or dim concert venue knows all too well the grainy, fuzzy outcomes of low-light imaging. Scientists trying to take images of biological specimens encounter the same issue because they tend to work in low light to avoid damaging delicate samples. The resulting grainy images can make it hard to distinguish the intricate proteins and internal structures they are trying to study.

The effect that causes grainy images of either your meal or a biological sample is called shot noise. Stanford researchers may have come up with an elegant solution to this problem, which they refer to as "multi-pass microscopy." This technique, detailed in a Sept. 27 paper in Nature Communications, could make it possible to view proteins and living cells in greater clarity than ever before.

"If you work at low-light intensities, shot noise limits the maximum amount of information you can get from your image," said Thomas Juffmann, co-author of the research and a postdoctoral research fellow in Stanford Professor Mark Kasevich's research group. "But there's a way around that; the shot-noise limit is not fundamental."

Recycled photons

In optical microscopy, individual units of light, called photons, strike a detector to make the image. The researchers have found they get better results if each photon interacts with the sample multiple times, even in low light. To implement this in a microscope, instead of sending light through a specimen and then directly capturing the resulting image, the Stanford team repeatedly reflects the image back onto the specimen.

"In a sense, it's like you're taking a picture of multiple times your object," said co-author Brannon Klopfer, a graduate student in the Kasevich group. "You first take an image of the specimen, you then illuminate it with an image of itself, and the image you get, you again send back to illuminate the sample. This leads to contrast enhancement."

Multi-pass microscopy is not the only approach to overcoming the shot-noise limit. Another method, called quantum microscopy, uses entangled photons to achieve the same result, but it is more challenging to carry out.

Entangled photons are photons that show quantum correlations. This means that performing an action on one of two entangled photons can have an effect on the other one, even if they are far apart from each other. It is what Albert Einstein referred to as "spooky action at a distance."

The ability of entangled photons to give information about each other means that quantum microscopy can produce higher-quality images compared to standard microscopy. At present, multi-pass microscopy has the potential to create comparably enhanced results with the added benefit of requiring less arduous preparation than quantum microscopy.

"The advantage you gain when entangling two photons is what we gain when we go through the sample twice," Juffmann said. "Currently, it is technologically easier to make a photon pass through a sample 10 times than to create a state in which 10 photons are entangled with each other."

A general technique

Multi-pass microscopy could boost more than just low-light imaging because it acts as a general signal-enhancing technique. The method can increase the sensitivity of various microscopy techniques, so long as a source of image noise doesn't build up with the recycling of photons.

"While multi-passing builds up the signal in your image, the noise is hardly affected," Klopfer said.

Read more at Science Daily

New movie screen allows for glasses-free 3-D

A new prototype display could show 3-D movies to any seat in a theater, with no eyewear required.

3-D movies immerse us in new worlds and allow us to see places and things that we otherwise couldn't. But behind every 3-D experience is something that is uniformly despised: those goofy glasses.

In a new paper, a team from MIT's Computer Science and Artificial Intelligence Lab (CSAIL) and Israel's Weizmann Institute of Science have demonstrated a display that lets you watch 3-D films in a movie theater without extra eyewear.

Dubbed "Cinema 3D," the prototype uses a special array of lenses and mirrors to enable viewers to watch a 3-D movie from any seat in a theater.

"Existing approaches to glasses-free 3-D require screens whose resolution requirements are so enormous that they are completely impractical," says MIT professor Wojciech Matusik, one of the co-authors on a related paper. "This is the first technical approach that allows for glasses-free 3D on a large scale."

While the researchers caution that the system isn't currently market-ready, they are optimistic that future versions could push the technology to a place where theaters would be able to offer glasses-free alternatives for 3-D movies.

Among the paper's co-authors are MIT research technician Mike Foshey; former CSAIL postdoc Piotr Didyk; and two Weizmann researchers that include professor Anat Levin and PhD student Netalee Efrat, who was first author on the paper. Efrat will present the paper at this week's SIGGRAPH computer-graphics conference in Anaheim, California.

How it works

Glasses-free 3-D already exists, but not in a way that scales to movie theaters. Traditional methods for TV sets use a series of slits in front of the screen (a "parallax barrier") that allow each eye to see a different set of pixels, creating a simulated sense of depth.

But because parallax barriers have to be at a consistent distance from the viewer, this approach isn't practical for larger spaces like theaters that have viewers at different angles and distances.

Other methods, including one from the MIT Media Lab, involve developing completely new physical projectors that cover the entire angular range of the audience. However, this often comes at a cost of reduced image resolution.

The key insight with Cinema 3D is that people in movie theaters move their heads only over a very small range of angles limited by the width of their seat. Thus, it is enough to display a narrow range of angles and replicate it to all seats in the theater.

What Cinema 3D does, then, is encode multiple parallax barriers in one display, such that each viewer sees a parallax barrier tailored to their position. That range of views is then replicated across the theater by a series of mirrors and lenses within Cinema 3D's special optics system.

"With a 3-D TV, you have to account for people moving around to watch from different angles, which means that you have to divide up a limited number of pixels to be projected so that the viewer sees the image from wherever they are," says Gordon Wetzstein, an assistant professor of electrical engineering at Stanford University who was not involved in the research. "The authors [of Cinema 3D] cleverly exploited the fact that theaters have a unique set-up in which every person sits in a more or less fixed position the whole time."

The team demonstrated that their approach allows viewers from different parts of an auditorium to see images of consistently high resolution.

Read more at Science Daily

Victim's Ghost Seen in Accident Photo? Unlikely

A photo taken at the scene of a fatal motorcycle crash in Kentucky has gone viral this week, with many claiming they can see the accident victim's spirit leaving his body.

The image, showing what seems to be a gray or white vertical form in the air above two ambulances, was photographed and shared on social media by Kentucky resident Saul Vazquez.

"I pulled over roll the passenger side window and snap the picture," Mr. Vazquez posted on his Facebook post of the photo, which as of today has nearly 9,000 shares.

A People magazine online article was headlined "Photo of Fatal Accident Become Online Sensation Over Claims It Shows Victim's Spirit." Others have suggested it's not a spirit but instead an angel. Stories of miracles or seemingly supernatural events at the scene of accidents are not uncommon; last year police officers who helped rescue a baby from an overturned car in a Utah river claimed that they heard an unexplained voice calling from the car—despite the fact that the mother had been dead for hours.

There are several reasons to suspect that the image may not be paranormal, but the best (and most obvious) reason to doubt that the whitish blur is the spirit of the accident victim appears in the news story about the incident: "He [the motorcylist] was transported to the hospital where he later died." Since the motorcyclist wasn't dead when the photo was taken, it would seem very unlikely that his spirit would be leaving his body at that time.

If spirits (or angels) can be photographed at scenes of tragic accidents—especially those involving many victims—then they should appear regularly. News photos and video of train, plane, and bus accidents, for example, should reveal ghostly images in and around the wreckage. In fact, if the soul leaves the body at death (as theology and ghost folklore suggest), then hospitals—not graveyards nor haunted houses—should be filled with ghosts and blurry white images in the hallways and emergency rooms.

The idea that the soul can somehow be quantified or recorded at the time of death goes back over a century. The most famous scientific experiment on that topic was conducted by Dr. Duncan MacDougall, who in 1907 tried to measure the weight of the soul. He weighed a half-dozen terminally ill patients before, during, and after death, concluding that there was an average of 21 grams difference in the weight of the bodies before and after death. His experiments were badly designed, however, with a tiny sample size and crude measurement tools. More modern measurements find no such effect, though the myth that the human soul weighs 21 grams remains today.

So if the vertical whitish thing in the photo isn't a ghost, what is it?

Vazquez has denied that the image has been altered, and there's no reason to think it has. It's much more likely to be an ordinary object that has taken on a spooky context because of the circumstances; in other words that same photo could likely have been taken at that same spot a day earlier, and no one would have associated it with anything odd or tragic.

Writer Hemant Mehta offered the following explanation on his blog: "It could easily be a discolored tree trunk. Seriously. I pulled up a Google Maps image of Highway 15 near Stanton, Kentucky where the accident took place. I don't know if this is the exact spot, but it was *very* easy to find a discolored tree trunk in the image."

It's difficult to tell what exactly the image is, but the image shows other foliage emerging from the shade of the trees in the same area; a tree trunk or light-colored branch is a real possibility. It could also be smoke from the wreck, though the motorcycle seems to be off to one side.

In any event, it's noteworthy that apparently no one at the scene reported seeing anything unusual, nor the supposed apparition just above them.

Read more at Discovery News