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UltravioletPhotography

Reference needed - spectral sensitivity of camera sensor to UV and IR


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I need a bit of help please folks. I'm looking for a reference for a paper I'm preparing which specifically pulls out the relative sensitivity of a typical bare camera sensor to UV and IR. I'm wanting to write a few lines on the need for complete IR blocking when doing UV reflectance imaging, so it would be great to be able to quantify the degree of the problem. Thanks.
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Unfortunately the camera maker(s) rarely make such information available to the general public. Some attempts to infer the spectral response by reverse engineering approaches are occasionally published, but mostly the results are questionable at best.

 

Astrophotography cameras however often disclose this kind of data. Example below from the Apogee Alta model range (backlit CCD). There are special UV models available too, and as can be seen from the chart below, some (for example, the F42 UV) with quite impressive UV response as well.

 

apogee UV.jpg

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That is interesting, thank you. I hadn't realised that some cameras could be made that sensitive to UV. I also got a reference from Klaus in Germany to one of the papers which he is an author on ("An attempt to push back frontiers - digital near-ultraviolet aerial archeology", GK Verhoeven, KD Schmitt, J. Archaeol. Sci., 37, 2010, 833-845) which gives the un-filtered responses of a Kodak CCD and CMOS sensor. This indicates that there is much more sensitivity towards IR than UV in the unfiltered sensors.
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The higher IR response is the expected normal behaviour. However, as seen in the graph I posted, with specially doped sensors one can sometimes have the better sensitivity shifted toward UV instead.

 

Unfortunately, the Apogee Alta F42 UV seems to be on the (very) pricey side, despite it only sporting about 4 MPix. This being a camera box without any finder also means it has to be tethered to a computer system in order to direct and focus the system. I guess despite such disadvantages, the F42 UV would do extremely well with a UV-Nikkor in front ... Then, there is the never-ending quest for a suitable UV bandpass filter and the requirement of keeping IR leakage under strict control.

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The sensor sensitivity under the Bayer filter depends on the Bayer dyes. Mostly? Entirely? So when you say "bare" sensor, do you mean without the Bayer layer?

 

Dan Llewellyn at MaxMax.com offers 4 sensor charts which show the IR region from 700-950nm and a small part of the UV region from 375-400nm. You should contact him to confirm how these measurements were made.

https://maxmax.com/f...ectral-response

 

Dan also removes the Bayer filter and may have some data about a truly "bare" sensor.

https://maxmax.com/m...ochrome-cameras

 

Quantum efficiency of Canon 30D sensor.

https://maxmax.com/maincamerapage/monochrome-cameras/more-tech

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Hi Andrea. Yes my terminology may have caused some confusion here. When I say bare sensor, I'm really meaning a commercial SLR sensor without the UV and IR blocking filter that it would come with as standard. I'll try following up with Dan too. Thanks.
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Cadmium, you got me to laughing with that one!! Our first official UV photography joke.

 

To non-US members -- There is a large genre of word-play jokes in the US which feature characters walking into a bar, sitting down and conversing with the bartender or with each other. I don't know if other countries or languages have these jokes?

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Andy Perrin

A Bare and a Bayer sit down at a Bar, one turns to the other and asks, "So, are you the sensitive type?"

 

I just about dyed.

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Andrea => We have similar bar jokes in France.

The most famous and shortest one is: "Un homme rentre dans un café, et plouf !" - "A man enters a café, plouf! (he drowns himself)".

It is a wordplay, here café is the drink (coffee), not the coffeshop that everybody would expect.

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Aha!! Thank you, Martin.

That's a good one!

(I remember just enough of my French to "get" it. :D )

 

*****

 

Perhaps I should split off the jokes from the main topic! :rolleyes:

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