Do digital sensors pick up UV and can it be filtered?

[IronWing]

I think I already have answer to my first question which is yes. I've been photographing fluorescent minerals (glow visible light under UV light source) lately and have been getting a blue wash over the specimens. It is most noticeable using long wave UV (368nm also called UV-A) and worse on flat surfaces facing the camera. I suspect that the camera sensor is picking up reflected UV light and interpreting it as blue. Would a UV haze filter on the lens cut the reflection?

Below is an extreme example. To the naked eye there is no blue showing on this specimen other than a few dust specs. I'm using a Nikon D90 and a Panasonic LX5 with similar results.

 

[blastingcap]

I think I already have answer to my first question which is yes. I've been photographing fluorescent minerals (glow visible light under UV light source) lately and have been getting a blue wash over the specimens. It is most noticeable using long wave UV (368nm also called UV-A) and worse on flat surfaces facing the camera. I suspect that the camera sensor is picking up reflected UV light and interpreting it as blue. Would a UV haze filter on the lens cut the reflection?

Below is an extreme example. To the naked eye there is no blue showing on this specimen other than a few dust specs. I'm using a Nikon D90 and a Panasonic LX5 with similar results.

Digital sensors are mostly, but not entirely, immune to UV light.

If you want a UV filter, try one with good multi-coatings and good blockage of UV light. The best choice for you is probably the cheap-but-effective Hoya HMC UV-0 aka UV(0). http://www.lenstip.com/index.php?art=113&roz=15 If you can't find that type, get the UV(c) instead; it's almost the same as the older UV(0) version except that the filter ring is thinner on the UV(c) type.

If you don't mind spending a little extra, I can recommend through personal experience the Hoya HD (harder, thinner, easier to clean version of the Hoya HMC). Unfortunately B+W filters do not block out enough UV light to make the cut, else I'd recommend those, too.

You can see the test results for other brands of UV filters here:

http://www.lenstip.com/113.4-article-UV_filters_test_Description_of_the_results_and_summary.html

 

[Railgun]

I use the Tiffen HT and so far it's proven fine.

 

[RobDickinson]

Yep , digital sensors usually have a UV filter on them. Its not 100% perfect so under strong UV you may need to add another.

Usually it is not needed, unless your rocking a leica m8.

 

[IronWing]

I have a couple old 1A and 1B skylight filters so I tried those separately and stacked with no noticeable improvement. I read that long exposure times can lead to a blue haze as well so I upped the ISO and cut exposure times, again without much change.

Thanks, Blastingcap. I read the article you linked and may try out the Hoya HMC UV-0. I also found the B+W 415 UV filter designed for fluorescence photography. It looks like it is exactly what I need but it is also four times the price of the Hoya.

http://www.bhphotovideo.com/c/produc...15_Strong.html

 

[GWestphal]

UV is the excitation wavelength and your camera sensor+typical UV filter will attenuate that to zero more or less. What you're seeing there is the emission wavelength which is probably about twice the wavelength. So, if you're trying to filter it out, you would need the appropriate filter for which ever mineral you're photographing, but then you'll be attenuating out any non-fluorescent (reflected, not emitted) light as well. Your camera picks it up during a long exposure even if you're not shining pure UV because most lights have a wide spectrum and contain some UV and that is exciting the fluorophores in the mineral producing the bluish cast.

 

[IronWing]

I tried the Hoya UV(0) filter and did almost no good at all. It only took me nine months but I finally figured it out tonight. It turns out that when one shoots brightly fluorescing objects under UV light that the white balance gets totally whacked. I haven't got the LX-5 there yet but the D90 is almost spot on.

Correct white balance on left, auto white balance on right. D90, 4sec, f8, ISO200, 105mm macro

 

[Throckmorton]

I've tested my Tiffen UV filter with a UV flashlight. It didn't work. UV gets through and makes fluorescent objects glow.

BTW your pictures are blurry

 

[IronWing]

I've tested my Tiffen UV filter with a UV flashlight. It didn't work. UV gets through and makes fluorescent objects glow.

BTW your pictures are blurry

I should clarify. The Hoya UV(0) blocked the shortwave UV pretty much completely and cut the longwave by maybe 80% (purely subjective eyeballing). It just did nothing to solve the blue cast problem.

 

[twistedlogic]

http://luminousminerals.com/greenland/uvphoto.shtml

From the little I gathered, the problem is that certain minerals will overexpose.

Also they mention that "your camera lens itself fluoresces."