The Amazing Gazania

[Andrea B.]

Col writes: A lot of the early UVIR-Cut filters only cut IR like the S8612.

 

Yes. And the S8612 and other BG type filters are sufficient for Visible shot use with an unmodified camera having a weak internal filter because IR contamination is the chief culprit in pinkish discoloured or washed out photos. Any UV contamination would probably, as mentioned, be very weak and likely only to show up in distance photos such as landscapes to create a hazy, bluish cast in some areas of the photo.

 

Using an BG filters for Visible shots on a broadband camera has its drawbacks. Maybe indoors you would not get too much UV contamination, but there are other problems with the colour which occur on the red side of the histogram. Each BG filter cuts the red differently, and it is possible to wind up with a blue-green cast to your photos. You cannot recover red which is not there. So take some care in how you choose a BG filter if you are going to try to use it on a broadband for your Visible work. And do always try to make a colour profile with the BG for colour correction use in your editor of choice.

 

At this point the Baader UVIR-Cut is the best we have (I think). Check the Filter Sticky for other UVIR-Cut options and read more there.

 

We are always interested in seeing posts with good comparative experiments involving these filters.

[msubees]

i think it is just because the CCDs are much less sensitive to UV. I figured that usually it takes 8-10 more EVs to expose with UV compared to VIS. so the UV wont show on your CCD even without a UV filter because it is about 1024 times less. this must be because sensitivities to UV is lower? I tried to google the proportion of UV in the sunlight compared to VIS, and i got 6% UV and 45% VIS, with the rest being IR. so UV:VIS is 1:7, not 1:1024 as show on CCD. thus CCD/CMOS must be about 100 times less sensitive to UV? of course there are also more loss of UV from the lens.

 

Damon, I think, is using an unmodified D70. This brings up something I have wondered about that and other such cams in the UV Sticky #1.

 

If usable/good unmodified for UV, how then is it able to take a Vis photo without at least UV blocking filter or a UVIR-Cut as you mentioned?

 

Sorry, I know this is a naive question but I have no history with these older CCD Nikons.

[Andrea B.]

Yes, there is less UV in Sunlight than there is Visible and IR

which is why longer exposures are needed to make UV photos when not using a supplementary UV flash.

 

But, as mentioned, you can get UV contamination of a Visible shot under certain circumstances

if the DSLR's internal filter is weak

or

if you are using a DSLR with no internal filter and an external filter blocking IR only.

 

The UV contamination in a Visible photo will show up as a haze or blue/violet cast - just as it did in film days -

and will happen mostly in landscape shots with a distant view.

It can also happen at high altitudes and with ocean shots.

I don't really recall all the possibilities, but there are probably a few more.

 

UV contamination is why so many "UV filters" used to be sold. They used to call them "haze filters".

 

It is probably unlikely that you would get UV contamination in Visible close-up flower work

when using a broadband DSLR and blocking IR only.

However you create another problem - a blue-green cast from your IR blocker.

 

So all things considered, it is probably a good idea to use a Baader UVIR-Cut filter for Visible shots made with a broadband cam.

Even with the Baader UVIR-Cut you still need to correct Visible colours but results are better.