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#151
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|GG| Lens profiling tool from Adobe ( for CS5 / LR / ACR).
Annika1980 wrote:
On May 11, 11:00 pm, "Bill Graham" wrote: The anti distortion software could be built right into the camera. In time, virtually all aberrations peculiar to lenses could be solved in software, and built into the cameras, couldn't they? Canon has already started doing that with it's Peripheral Illumination Correction built into the Fab 5D2 and the 50D. I suppose in future releases we will see correction for other lens aberrations. http://www.usa.canon.com/dlc/control...articleID=2027 So has Nikon but I wish they'd make it more accessible to raw converters because that's worthless shooting raw without their (paid) software. grumble |
#152
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Lens profiling tool from Adobe ( for CS5 / LR / ACR ).
"Mxsmanic" wrote in message
... David J Taylor writes: IASI: http://smsc.cnes.fr/documentation/IA.../SPIE_ASPI.pdf Still looks like one photosite = one number. Three detectors provide three (optically coincident?) photosites, each of which provides one signal level per pixel, if I'm reading the poorly-written publication correctly. The spectrum at each pixel is analysed, producing over 8000 value per pixel. I looked for a better description but didn't find one quickly. Cheers, David |
#153
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Lens profiling tool from Adobe ( for CS5 / LR / ACR ).
"David J Taylor" wrote:
"Mxsmanic" wrote in message .. . David J Taylor writes: IASI: http://smsc.cnes.fr/documentation/IA.../SPIE_ASPI.pdf Still looks like one photosite = one number. Three detectors provide three (optically coincident?) photosites, each of which provides one signal level per pixel, if I'm reading the poorly-written publication correctly. The spectrum at each pixel is analysed, producing over 8000 value per pixel. I looked for a better description but didn't find one quickly. I read through the cite provided, and saw nothing indicating 8000 values per pixel. It might well be that the final product distributed to others does indeed have that resolution, just that the cited paper did not say that. What it does say is that each set of pixel data from the sensor is a 3 channel 16 bit sample. That is, 48 bits, or 2.8e+14 values per bit. Regardless of that it is a terrific example to show what is wrong with the various naive statements made by Mxsmaniac on this topic. If one wants to build a sensor/camera to produce photographs that will be similar to what the human eye can see, the technology and engineering will necessarily be distinctly different than a sensor/camera that is designed to produce spectrographics. They both do basically the same things, and use similar modular parts (encoding filters, sensors, ADC's, etc), but the parameters for each are necessarily very different to match the design target. Interferometers rather than Bayer filters, slower ADC's with multiple scans at different ISO gains to achieve higher bit density, and an entirely different post processing toolset are the obvious differences. But they are all equivalents, the data chain is the same, and it is clear that three channel "color" sensor data can indeed define a continuous spectrum of wavelengths, even into the IR region. -- Floyd L. Davidson http://www.apaflo.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
#154
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Lens profiling tool from Adobe ( for CS5 / LR / ACR ).
On 5/15/2010 2:23 AM, David J Taylor wrote:
"Mxsmanic" wrote in message ... David J Taylor writes: IASI: http://smsc.cnes.fr/documentation/IA.../SPIE_ASPI.pdf Still looks like one photosite = one number. Three detectors provide three (optically coincident?) photosites, each of which provides one signal level per pixel, if I'm reading the poorly-written publication correctly. The spectrum at each pixel is analysed, producing over 8000 value per pixel. I looked for a better description but didn't find one quickly. The authors are writing for a specialist audience, people who do optical interferometry or design satellites for a living. They're assuming that one already understands the technology and are pointing out the details of their particular implmentation. Another paper, describing an earlier satellite that uses a similar sensor, is http://www.atmos-chem-phys.net/8/2151/2008/acp-8-2151-2008.pdf. The keyword you need is "FTIR" or "Fourier Transform Infrared spectrometer". There's a tutorial at http://www2.fc.up.pt/pessoas/peter.eaton/tutorial/webCT/index.html that includes a brief discussion of the technology and instructions for operating a specific instrument. A more detailed discussion can be found at http://spectroscopy.lbl.gov/FTIR-Martin/ Saying that "the spectrum is analyzed" implies that some kind of magic is done with a single data point to derive 8000 values. It doesn't work that way--the whole system is purpose made to provide a spectrum, using moving parts and series of measurements, it's not something done in post as an afterthought. An FTIR uses a moving mirror to generate a range of values over time by altering the optical path length. What you get is the fourier transform of the spectrum--you have to do calculations on that to get the actual spectrum. The whole thing is really quite clever. At each point in time the sensor gives a single value. Over a movement cycle of the mirror it will give some wide range of them, what that range is, specifically, will depend on the rate at which the mirror is moving and the response time and resolution of the sensor. But all the sensor measures is intensity. |
#155
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|GG| Lens profiling tool from Adobe ( for CS5 / LR / ACR ).
"Paul Furman" wrote in message
... Annika1980 wrote: On May 11, 11:00 pm, "Bill Graham" wrote: The anti distortion software could be built right into the camera. In time, virtually all aberrations peculiar to lenses could be solved in software, and built into the cameras, couldn't they? Canon has already started doing that with it's Peripheral Illumination Correction built into the Fab 5D2 and the 50D. I suppose in future releases we will see correction for other lens aberrations. http://www.usa.canon.com/dlc/control...articleID=2027 So has Nikon but I wish they'd make it more accessible to raw converters because that's worthless shooting raw without their (paid) software. grumble I share your wish. But, I don't agree though that raw shooting makes no sense unless you use CaptureNX. Raw still allows a lot more adjustments in PS, with significantly less data loss than jpeg or tiff. -- Peter |
#156
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|GG| Lens profiling tool from Adobe ( for CS5 / LR / ACR ).
On Fri, 14 May 2010 22:43:14 -0700, Paul Furman
wrote: So has Nikon but I wish they'd make it more accessible to raw converters because that's worthless shooting raw without their (paid) software. grumble Bibble has had lens correction for a while. First PTLens, then it's own implementation. |
#157
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|GG| Lens profiling tool from Adobe ( for CS5 / LR / ACR ).
In message , Paul Furman paul-
@-edgehill.net writes Annika1980 wrote: On May 11, 11:00 pm, "Bill Graham" wrote: The anti distortion software could be built right into the camera. In time, virtually all aberrations peculiar to lenses could be solved in software, and built into the cameras, couldn't they? Canon has already started doing that with it's Peripheral Illumination Correction built into the Fab 5D2 and the 50D. I suppose in future releases we will see correction for other lens aberrations. http://www.usa.canon.com/dlc/control...Act&articleID= 2027 So has Nikon but I wish they'd make it more accessible to raw converters because that's worthless shooting raw without their (paid) software. grumble There is a whole load of software that works with Nikon Raw. What are you grumbling about? -- \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ \/\/\/\/\ Chris Hills Staffs England /\/\/\/\/ \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ |
#158
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Lens profiling tool from Adobe ( for CS5 / LR / ACR ).
Mxsmanic wrote:
Floyd L. Davidson writes: What it does say is that each set of pixel data from the sensor is a 3 channel 16 bit sample. That is, 48 bits, or 2.8e+14 values per bit. So three numbers, just like RGB. That's hardly going to record a full spectrum. Wrong. Regardless of that it is a terrific example to show what is wrong with the various naive statements made by Mxsmaniac on this topic. If one wants to build a sensor/camera to produce photographs that will be similar to what the human eye can see, the technology and engineering will necessarily be distinctly different than a sensor/camera that is designed to produce spectrographics. They both do basically the same things, and use similar modular parts (encoding filters, sensors, ADC's, etc), but the parameters for each are necessarily very different to match the design target. A spectrograph needs to scan the entire spectrum for each pixel, producing a very large set of individual numbers that represent the signal strength at each of many frequencies. It cannot capture the original spectrum completely without an infinite number of samples, but it can do vastly better than a single photosite on a digital camera imaging sensor. In that particular case they were doing 55,000 samples. You either didn't read the cited article or couldn't understand it. The photosite of a sensor produces only one number, which represents the integration of all frequencies present in the original scene, the sum of the products of signal strength in the original scene at each frequency and the sensitivity at that frequency in the sensor. This integration produces just one number, and it's a one-way transformation. It is impossible to reconstruct the original spectral distribution of the scene from this single number, because multiple distributions can produce the same number. Wrong. In fact, the spectrograph is the inverse of the digital imaging sensor. The spectrograph produces a very large set of numbers for the entire image as a whole, giving its overall frequency distrubtion--but it provides no detail information, effectively treating the entire image as a single pixel. The sensor in a camera is exactly the opposite, capturing a great many pixels in order to record detail, but recording only a tiny fraction of the spectral data for each pixel. Hence it is abjectly ridiculous of you to claim that because a photographic camera does not produce spectrographs that it cannot see and respond to the entire spectrum of light. With a spectrograph, you can reverse the process and get a pretty good approximation of the original spectral distribution, but you get no detail, just a complete blur (just one pixel). With a digital camera, you can reverse the process and get a pretty good approximation of the original image detail, but virtual all the spectral information is gone. Wrong. The digital camera works because human beings concentrate on detail, not spectra. But the fact remains that, once the image is captured, virtually all the spectral information is gone, which means that anything that depends on the original spectrum cannot be simulated in post production. Again, wrong. Once the the *data* is capture, it is used to produce a photographic image. It could just as well be used to produce a spectrograph. This also applies to certain lens effects, such as blurring and transmission characteristics, or anything that removes information from the original scene. Well, isn't that sort of a broad statement if we've ever seen one! And totally meaningless, too! But they are all equivalents, the data chain is the same, and it is clear that three channel "color" sensor data can indeed define a continuous spectrum of wavelengths, even into the IR region. Nope. With only three numbers, a many-into-one conversion of all possible spectra into all possible number sets occurs, and it is irreversible, so the original spectrum cannot be recreated. Untrue. -- Floyd L. Davidson http://www.apaflo.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
#159
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Lens profiling tool from Adobe ( for CS5 / LR / ACR ).
Bruce wrote:
On Thu, 13 May 2010 22:47:52 -0700, "Bill Graham" wrote: I was not aware that there had been an increase in the sales of tilt-shift lenses in recent years, but there could be several reasons for this.....Perhaps the price has come down a lot? Or perhaps there has been a resurgence in architectural photography. Or perhaps there are other things that tilt-shift lenses will do that I am unaware of that can't be done in Photoshop Yes, that's it. Correctly used, a tilt-shift lens can provide exceptional depth of field that would be virtually impossible to replicate in software. You can achieve quite a lot by shooting several shots of the same scene focused at different distances, and then combining elements of those images, but the results look very different and quite artificial. Focus stacking works fine at non-macro distances. It's rare to see people use that method but it works great. As for using Photoshop to eliminate converging verticals, as Mxmanic has explained (correctly, but too many times!) there is a huge loss of image quality. I am very well acquainted with the picture editor of an architectural magazine He summarily rejects any shot submitted for publication where converging verticals have been corrected in software. He says he can spot them a mile away, and I believe him. I have tried very hard to hoodwink him but without success ... I suppose there are subtle cues, but a small amount of correction is hardly noticeable. The bigger problem is without a shift lens, you can't frame the composition and don't know what it's going to look like till later. Shift lenses also have a trade-off of resolution because you are using the edge of a larger image circle, it will be a little softer and show some vignetting. -- Paul Furman www.edgehill.net www.baynatives.com all google groups messages filtered due to spam |
#160
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Lens profiling tool from Adobe ( for CS5 / LR / ACR ).
"Mxsmanic" wrote in message
... David J Taylor writes: The spectrum at each pixel is analysed, producing over 8000 value per pixel. Eight thousand separate numbers, or a number that can have 8000 different values? In the first case, explain how it is doing this with only three sensors. Please take a look at J. Clarke's explanation of "Fourier Transform Infrared spectrometer". It's not a three sensor camera. Cheers, David |
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