Is there a (simple) way to get at a particular camera sensors spectral sensitivities? / Roger -----Original Message----- From: colorsync-users-bounces+graxx=videotron.ca@lists.apple.com [mailto:colorsync-users-bounces+graxx=videotron.ca@lists.apple.com] On Behalf Of Ben Goren Sent: 15 mars 2016 12:07 To: ColorSync <ColorSync-Users@lists.apple.com> Subject: Re: Colorsync-users Digest, Vol 13, Issue 76 On Mar 14, 2016, at 6:08 PM, Graeme Gill <graeme2@argyllcms.com> wrote:
Certainly the issues that Anders Torger has tripped across in developing his own DNG profilng solution (DCamProf) reenforce the view that there is some odd hard coded behavior in DNG.
Anders has independently developed a very similar approach to mine, starting with a spectral model of the camera sensor. If you want the least-worst DNG profile you're going to get, you need to use DCamProf. And it's an open source labor of love with not much attention paid to user friendliness -- good results if you're willing to invest in the learning curve. But even at its best...you're still stuck with the bizarre illuminant nonsense that does this automatically-estimated blending between A and D50 with no meaningful user control nor input. Again, horses for courses. I can't imagine a _Sports_Illustrated_ or _National_Geographic_ photographer having any non-idle interest in my workflow. Lightroom and DNG is a great solution for those photographers -- and, indeed, for the overwhelming majority of photographers. You'd be hard pressed to better, even theoretically -- and anything you could do better in theory would have been impractical or impossible with the hardware on the market at the time it was developed. But just because Adobe products are excellent for most photographers doesn't mean that they're excellent for everybody. And, indeed, when it comes to colorimetric reproduction, they're no more suited to the job than Excel is to being a distributed relational database server. Cheers, b&
Is there a (simple) way to get at a particular camera sensors spectral sensitivities?
Simple, yes. Cheap, not so much. But sacrificing accuracy (still being within most of the practical needs), those can be restored from a shot of CC SG. Problem is, those spectral characteristics depend on temperature and heat distribution across the sensor. -- Best regards, Iliah Borg LibRaw, LLC www.libraw.org www.rawdigger.com www.fastrawviewer.com
On Mar 15, 2016, at 9:39 AM, Roger Breton <graxx@videotron.ca> wrote:
Is there a (simple) way to get at a particular camera sensors spectral sensitivities?
Simplest is to get it from somebody else. Cheap is to build your own large-sized spectroscope, photograph a spectrum, and combine it with various other measurements and math and what-not. I still need to type up and post instructions and plans and what-not. But the basic idea is that if you know the SPD reaching the sensor (which is a product of the illuminant and the efficiencies of everything between the illuminant and the sensor -- presumably, just the diffraction grating and the lens) then you can treat the rainbow image as a standard chart image to get your RGB values. Assuming the sensor is linear (a good assumption if your capture technique is impeccable), that's your spectral sensitivity. Cheers, b&
sin 4 On Tuesday, March 15, 2016, Ben Goren <ben@trumpetpower.com> wrote:
On Mar 15, 2016, at 9:39 AM, Roger Breton <graxx@videotron.ca <javascript:;>> wrote:
Is there a (simple) way to get at a particular camera sensors spectral sensitivities?
Simplest is to get it from somebody else.
Cheap is to build your own large-sized spectroscope, photograph a spectrum, and combine it with various other measurements and math and what-not. I still need to type up and post instructions and plans and what-not. But the basic idea is that if you know the SPD reaching the sensor (which is a product of the illuminant and the efficiencies of everything between the illuminant and the sensor -- presumably, just the diffraction grating and the lens) then you can treat the rainbow image as a standard chart image to get your RGB values. Assuming the sensor is linear (a good assumption if your capture technique is impeccable), that's your spectral sensitivity.
Cheers,
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participants (4)
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Ben Goren
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edmund ronald
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Iliah Borg
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Roger Breton