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,
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