UV camera project build question

ProfHankD wrote:

petrochemist wrote:

ProfHankD wrote:

It's not really intended for UV nor for use with cameras, but you can get a theatrical gel filter color swatch book quite cheaply and each filter comes with its spectral profile. Take a look at Rosco's web site to see some profiles -- for example:

Combining two or three filters from a Rosco pack might get you close enough to what you want in UV sensitivity. For example, the above + #375 Cerulean Blue might not be a bad starting point, although you'll be down more than 2 stops around 400nm (and lower elsewhere). Of course, you'll probably need longish exposures and a bright UV light -- and bright UV lights are seriously dangerous.

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Typical camera sensors being designed to capture visible light are not particularly sensitive to UV, but are sensitive to NIR - the reason a hot mirror is installed. The rise at the right of the spectra You've supplied shows considerable NIR is transmitted by this gel - FWIW I've not found any gels (other than diffusion ones) that don't transmit NIR well though I've only run about 50 of them on the spectrometer at work. Nearly all transmit more throughout the NIR (700-1100nm) than they do at any visible wavelength. They're definitely good for IR photography!

Like I said, you stack 2-3 gels to get the desired profile. According to Rosco, there are definitely gels that kill at least to 740nm. Look at the spectral profiles -- for example, of the #375 Cerulean Blue that I mentioned as a potentially good pairing:

Notice that at least out to 740nm it's flat at 0% transmission. That plus the usual NIR blocking should take care of NIR pretty well... assuming this doesn't take care of it by itself, which it might. Have you tried any of the gels that claim to kill this range of wavelengths?

Stack that with the other one and you'll get a pretty nice peak around 400nm. Actually, there are probably better pairs in the $2 sampler book, but I just picked two that were easy to find and reasonable rather than paging through all to find the best pair.

Not saying it's perfect, but we're talking about the OP modifying a camera worth less than $25 -- this is obviously a cheap and dirty project.

To get UV response you have to remove the hot mirror, which is what stops the sensor picking up 700-1100nm 740 is no good. Of the 50 I tested a handful were low transmission in the 700region but these all transmitted over 30% at 750nm (I've only got tabulated data readily to hand).

My other gel booklet which happens to be on my desk has #375 Cerulean Blue. It's visible light transmission is considerable - I'll check the full spectra in a bit.

To record UV you're going to need all wavelengths from 400-1100nm blocked to under 1% I don't see it helping much!