I have an OceanOptics USB4000 with a radiometrically calibrated tungsten light source too. Could that help? / 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: 16 mars 2016 12:50 To: ColorSync <colorsync-users@lists.apple.com> Subject: Re: Spectral sensivities On Mar 16, 2016, at 9:36 AM, Wüller Dietmar <dwueller@gmx.de> wrote:
The easiest and cheapest way to get spectral sensitivities for a single device is to have it measured as a service.
Easiest, maybe, but certainly not cheapest. And perhaps not best, either. The bill of materials for a suitable spectroscope is under $20. You'll need to know the transmission efficiency of the diffraction grating, and the least-worst way to get that is with a monochromator...but you can get a monochromator for cheap off FleaBay, and a spectroscope design can be adapted to a monochromator design if you want to continue the dirt-cheap route. And virtually nobody I'm aware of (with one notable exception who's reading these words (Hi Iliah!)) takes the lens into consideration when determining a camera's spectral sensitivities. Some lenses have rather complex spectral absorption characteristics. If you must use a lens, use Canon's "Plastic Fantastic" 50mm f/1.8; its transmission is as spectrally flat as you'll find in any lens and significantly flatter than many, including lots of top-of-the-line L glass. But if your commercial service (or whatever) assumes that the optics are spectrally flat, you've got the lens permanently "baked into" all your data. Cheers, b& _______________________________________________ Do not post admin requests to the list. They will be ignored. Colorsync-users mailing list (Colorsync-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/graxx%40videotron.ca This email sent to graxx@videotron.ca
of course, one can always measure the lens. :) there is only one iliah. maybe he could be cloned, and rented out to all industry actors ... Emund On Thursday, March 17, 2016, Roger Breton <graxx@videotron.ca> wrote:
I have an OceanOptics USB4000 with a radiometrically calibrated tungsten light source too. Could that help?
/ Roger
-----Original Message----- From: colorsync-users-bounces+graxx=videotron.ca@lists.apple.com <javascript:;> [mailto:colorsync-users-bounces+graxx <javascript:;>= videotron.ca@lists.apple.com <javascript:;>] On Behalf Of Ben Goren Sent: 16 mars 2016 12:50 To: ColorSync <colorsync-users@lists.apple.com <javascript:;>> Subject: Re: Spectral sensivities
On Mar 16, 2016, at 9:36 AM, Wüller Dietmar <dwueller@gmx.de <javascript:;>> wrote:
The easiest and cheapest way to get spectral sensitivities for a single device is to have it measured as a service.
Easiest, maybe, but certainly not cheapest. And perhaps not best, either.
The bill of materials for a suitable spectroscope is under $20. You'll need to know the transmission efficiency of the diffraction grating, and the least-worst way to get that is with a monochromator...but you can get a monochromator for cheap off FleaBay, and a spectroscope design can be adapted to a monochromator design if you want to continue the dirt-cheap route.
And virtually nobody I'm aware of (with one notable exception who's reading these words (Hi Iliah!)) takes the lens into consideration when determining a camera's spectral sensitivities. Some lenses have rather complex spectral absorption characteristics. If you must use a lens, use Canon's "Plastic Fantastic" 50mm f/1.8; its transmission is as spectrally flat as you'll find in any lens and significantly flatter than many, including lots of top-of-the-line L glass. But if your commercial service (or whatever) assumes that the optics are spectrally flat, you've got the lens permanently "baked into" all your data.
Cheers,
b& _______________________________________________ Do not post admin requests to the list. They will be ignored. Colorsync-users mailing list (Colorsync-users@lists.apple.com <javascript:;>) Help/Unsubscribe/Update your Subscription:
https://lists.apple.com/mailman/options/colorsync-users/graxx%40videotron.ca
This email sent to graxx@videotron.ca <javascript:;>
_______________________________________________ Do not post admin requests to the list. They will be ignored. Colorsync-users mailing list (Colorsync-users@lists.apple.com <javascript:;>) Help/Unsubscribe/Update your Subscription:
https://lists.apple.com/mailman/options/colorsync-users/edmundronald%40gmail...
This email sent to edmundronald@gmail.com <javascript:;>
That's a really neat toy! It would probably be very good for measuring the spectral transmission efficiency of a camera lens, though the resolution is going to be serious overkill. (But downsampling is easier / better than extrapolating.) In practice, a consumer spectrometer is the only exotic equipment you need, and the i1 Pro is perfect for the job. b&
On Mar 16, 2016, at 5:25 PM, Roger Breton <graxx@videotron.ca> wrote:
I have an OceanOptics USB4000 with a radiometrically calibrated tungsten light source too. Could that help?
/ 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: 16 mars 2016 12:50 To: ColorSync <colorsync-users@lists.apple.com> Subject: Re: Spectral sensivities
On Mar 16, 2016, at 9:36 AM, Wüller Dietmar <dwueller@gmx.de> wrote:
The easiest and cheapest way to get spectral sensitivities for a single device is to have it measured as a service.
Easiest, maybe, but certainly not cheapest. And perhaps not best, either.
The bill of materials for a suitable spectroscope is under $20. You'll need to know the transmission efficiency of the diffraction grating, and the least-worst way to get that is with a monochromator...but you can get a monochromator for cheap off FleaBay, and a spectroscope design can be adapted to a monochromator design if you want to continue the dirt-cheap route.
And virtually nobody I'm aware of (with one notable exception who's reading these words (Hi Iliah!)) takes the lens into consideration when determining a camera's spectral sensitivities. Some lenses have rather complex spectral absorption characteristics. If you must use a lens, use Canon's "Plastic Fantastic" 50mm f/1.8; its transmission is as spectrally flat as you'll find in any lens and significantly flatter than many, including lots of top-of-the-line L glass. But if your commercial service (or whatever) assumes that the optics are spectrally flat, you've got the lens permanently "baked into" all your data.
Cheers,
b& _______________________________________________ Do not post admin requests to the list. They will be ignored. Colorsync-users mailing list (Colorsync-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/graxx%40videotron.ca
This email sent to graxx@videotron.ca
Dear Roger, You can pick a light sphere for cheap than, and use the second port to mount a photodiode or spectrophotometer (i1 spectro is OK; but you can also use a Hamamatsu C12666MA or C12880MA, those are cheaper and can be mounted permanently). I use xenon flash as light source with C12880MA, to eliminate long exposures and thus avoid heat / long exposure noise problems. With tungsten source a photodiode or C12666MA is quite OK; but if a photodiode is used an additional calibration task is needed. On Mar 16, 2016, at 8:25 PM, Roger Breton wrote:
I have an OceanOptics USB4000 with a radiometrically calibrated tungsten light source too. Could that help?
/ Roger
-- Best regards, Iliah Borg LibRaw, LLC www.libraw.org www.rawdigger.com www.fastrawviewer.com
participants (4)
-
Ben Goren
-
edmund ronald
-
Iliah Borg
-
Roger Breton