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Refocusable Plenoptic Light-Field Photography
virgil_disgr4ce writes "Wired is reporting that a Stanford student using about 90,000 microlenses has developed a plenoptic camera whose images can be refocused, via software, after they are exposed." From the article: "'We just think it'll lead to better cameras that make it easier to take pictures that are in focus and look good,' said Ng's adviser, Stanford computer science professor Pat Hanrahan."
I'm curious... how adjustable is the post-processing focusing? E.g. depth of field, f/stop, etc. Do you basically get to adjust ANY of that after the image is recorded?
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I wonder if the image data gathered by such a camera could somehow be transformed into basic 3d depth information. If so, this could be the beginning of 3D imaging for the consumer.
Having seen this stuff in action first hand, it's cool as heck. Also a tad scary. Miniblinds not closed 100% then you can see in, tree in the way no problem.
Basically what we see as solid with 2 eyes, may not be solid at all. So much like the IR/UV cameras, this new toy has a dark side.
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The linked article comments that there's an effective loss of resolution, but goes no further.
Obviously taking a camera that's designed to record light intensity and modifying it to record light intensity and direction isn't free. In the worst case, you're decreasing your effective resolution by the number of new lenses, or by a factor of 90,000. I don't think that's quite what happens though, because many of these lenses will be recording essentially the same information, and while only one may be perfectly focussed on part of the frame, nearby lenses can probably contribute color and intensity information as well. If we assume a 2Mpixel image is "good", the article's comment that the student's using a 16Mpixel camera but that an 8Mpixel camera might be good enough seems to support a roughly 4x to 8x decrease in effective resolution. Can the poster who claims to have heard the actual discussion at Siggraph comment?
That's a high price to pay for not having to use the viewfinder. It's cool tech, and I'm sure there are practical uses for it somewhere, but I don't think consumer cameras are the place for it just yet.
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The next step is to pair the cameras and the LED image emitters, similar to night-vision goggles, to make a really kewl pair of corrective lenses. Truly the ultimate nerdwear!
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You could always go to a pin hole camera and eliminate the problem entirely. Alright so you'd need 10,000 ASA film or .1 lux for video but focas would never be an issue. Always been a massive fan of pin hole cameras. It's also a handy trick for those of us with failing eyesight for reading fine print. There have also been lensless cameras that use a rotating slit. There are 360 cameras that use the principal. Fun with optics
By the way, in case somebody doubts this, I did this in 1996 and used my mac laptop to compute the refocused image. I was experimenting with imaging from earth imaging sattelites. I still have the code, which actually was a relatively slow script written in Igor Pro.
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That's not completely fair. If I understand you, what you're saying is that in fact you DO lose resolution, but the loss in resolution can be compensated for by higher-resolution sensors and because you don't have to increase the physical size of the sensor, the production costs won't go up too much. I don't know enough about CCDs and CMOS sensors to know what the probable increase in cost would be, but it sounds fairly minor. At least for CPUs, I know die size is a stronger indicator of manufacturing cost than transistor count, though the latter obviously plays a role.
The other problems that you've swept under the rug seem to me to be more important, at least in the near term. If you take a CCD and replace each of its sensor sites with a 12x12 array, as you suggest, you're talking over a 100-fold increase in the data to be processed. While I haven't read the technical papers on the subject, it seems like the processing is more complicated than the processing that goes on in a standard digicam, which probably means at least a 200x increase in processing requirements. If you wait for Moore's law to save you, that's 10 years. Budgeting for a more expensive image processor will shave maybe a year or two off that number, but it's still fairly long-term research.
You could reduce the processing needed in-camera by storing closer-to-raw data and doing the processing at a workstation later, but then you have the problem of a data stream that's ~100x as large. Even with very fast flash storage, that would take 30+ seconds to write a single image, and you could only fit a few onto a 1GB card. Also, you introduce the problem that the photographer doesn't get feedback as to what he or she actually shot, and unless you can also post-process to correct for motion blur, abberation in color, etc. you still need that functionality.
It all sounds interesting, and I applaud research into what useful things could be done with likely future technology, but (and maybe I'm misreading the situation) it sounds like the core research is being cast as a thing we could be doing RSN, which I highly doubt. As a technique to make use of sensor densities that would normally exceed the capabilities of the lens they're attached to in order to do something useful, this is interesting. As a technique to be applied to today's or near-future sensors and cameras, I find it less interesting.
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Could this be used to sharpen what we see in an x-ray image of a person? Take an x-ray of the whole body and then refocus to concentrate on one particular cross-sectional plane?
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If you look at the sample images, you can see the type of image that will be "helped" by their camera...
Auto focus cameras have to focus on something... and many times I've had them focus on the wrong thing. There isn't really anything you can do at that point except reshoot.. or use the system such as they describe.
This would be of great value to me, I have many photos where the image is otherwise perfect except the focus point is off.
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