Re: Spectral sensivities
Re: Spectral sensivities
- Subject: Re: Spectral sensivities
- From: Ben Goren <email@hidden>
- Date: Wed, 16 Mar 2016 18:21:35 -0700
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 <email@hidden> 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=email@hidden [mailto:colorsync-users-bounces+graxx=email@hidden] On Behalf Of Ben Goren
> Sent: 16 mars 2016 12:50
> To: ColorSync <email@hidden>
> Subject: Re: Spectral sensivities
>
> On Mar 16, 2016, at 9:36 AM, Wüller Dietmar <email@hidden> 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&
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