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UltravioletPhotography

UVIVF Possible Visible Light Leak?


cdhgamer

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Jonathan, Thanks for that scan. I got the graphs from them. They have them, just not anywhere in their webpages evidently.

Seems like neither of those are that great to use for a UV cut barrier lens filter for UVIVF ?

I also have a Zeiss T* UV filter. Have not tried it for much yet, can't find the graph for it online at the moment, but I think I saw it online once.

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Ulf. Good idea. I'll try that next time I've got the equipment on.

 

Steve. Ah right. At least they have the data. As for use for a UV cut for UVIVF, I suppose it depends how the light source itself is filtered (and what the source is). But yes, I'd want something with a higher cut-off for fluorescence myself. Some Zeiss T* UV filter data;

https://www.lensrentals.com/blog/2017/09/looking-at-clear-and-uv-filter-spectrograms/

 

Not the best graph, but might be worth a try.

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Ulf. Good idea. I'll try that next time I've got the equipment on.

 

Steve. Ah right. At least they have the data. As for use for a UV cut for UVIVF, I suppose it depends how the light source itself is filtered (and what the source is). But yes, I'd want something with a higher cut-off for fluorescence myself. Some Zeiss T* UV filter data;

https://www.lensrent...r-spectrograms/

 

Not the best graph, but might be worth a try.

 

Well, the light source will have UV in it, if you want to block reflected UV from entering the lens (for UVIVF shots) then it is best to do that above 400nm, even 420/435nm.

The KV-418 works nice, if you can find one.

If the Baader UV/IR-Cut filter leaks UV, and that is a concern, then it looks like you will get slightly more UV leaking with either of these Firecrest filters.

I tried Baader UV/IR-Cut stacked with GG420 and GG435 behind the Baader (between the Baader and the camera lens), and that worked good for me.

 

Here is where I first heard about the Zeiss T*.

http://www.ultraviol...dpost__p__25416

 

I saw a graph of it somewhere, which I can't find right now, which looked better than the one on the page you linked to above.

There is probably some UV/IR cut or UV cut filter that does cut slightly above 400nm, don't know.

 

Frankly, if some has the Baader UV/IR-Cut, I might try the GG420/435 between the Baader and the lens.

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Well, the light source will have UV in it, if you want to block reflected UV from entering the lens (for UVIVF shots) then it is best to do that above 400nm, even 420/435nm.

The KV-418 works nice, if you can find one.

If the Baader UV/IR-Cut filter leaks UV, and that is a concern, then it looks like you will get slightly more UV leaking with either of these Firecrest filters.

I tried Baader UV/IR-Cut stacked with GG420 and GG435 behind the Baader (between the Baader and the camera lens), and that worked good for me.

 

Here is where I first heard about the Zeiss T*.

http://www.ultraviol...dpost__p__25416

 

I saw a graph of it somewhere, which I can't find right now, which looked better than the one on the page you linked to above.

There is probably some UV/IR cut or UV cut filter that does cut slightly above 400nm, don't know.

 

Frankly, if some has the Baader UV/IR-Cut, I might try the GG420/435 between the Baader and the lens.

 

 

Thanks everyone for your continued interest in this, sorry I was away for a bit but I currently am taking care of two family members who are recovering from surgeries so I've been away from my computer.

 

 

Cadmium, I shot with the 400 nm Firecrest the other night and didn't see much difference honestly. The dark room I've been shooting in has a few walls that are white, would those be causing possible UV reflection then that's tinting the flowers a more purple/blue? Obviously I'd be interested in trying higher nm filtering, but just curious on contamination there.

 

 

Addition to preceding.

 

Todd, two things.

 

I have a D810. I could try to make a UVIVF white balanced NEF with my Convoy and make it available for you to load into your camera to use as a WB setting. (Do you know how to do that?) I wonder if this would be useful or help?

 

If you can arrange for me to download a raw NEF of your flower, I'll run it through Raw Digger and see whether any red is being recorded in the chlorophyll area. And I can try other converters for you to see if they bring out the red. Let me know.

 

 

Andrea, that would be fantastic if you could make that white balance NEF, do you suppose that would also work if I color matched it in the curves tool of photoshop for the midtones? I can always do it the other way, but I'm just curious.

 

 

I also am not able to include the raw file in the forum's file system, there's a 30 MB global upload limit and the file is 36MB, so I'll include it in a Dropbox link. The red fluor wasn't crazy on the stamen by the way, but not too subtle to notice either.

 

 

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Thank you for sharing the raw file.

 

I made a quick check with white balancing it with FastRawViewer https://www.fastrawviewer.com/ and posting screen shots.

The program is an excellent raw-viewer.

For good final conversion other programs are needed.

 

By selecting different points for the white balance I get different results.

There might be one similar to what you saw when shooting the image.

 

1:

post-150-0-47081700-1551847516.png

 

2:

post-150-0-09532700-1551847478.png

 

3:

post-150-0-94771200-1551847490.png

 

4:

post-150-0-75779500-1551847546.png

 

5:

post-150-0-24459400-1551847533.png

 

Edit: Added number labels to the pictures.

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I finally had some time to look at the lily photo. I am sorry it took so long! I've had my hands full with domestic matters for the last couple of months.

 

Here is the original conversion in which a Daylight white balance was applied.

lily.jpg

 

 

This is the Raw Digger "raw composite" which has had no color corrections applied (i.e., no white balance). This shows us that there were really no visible red emissions recorded from the flower itself. In the deep shadows around the flower, there was some red fluorescence recorded from the chlorophyll of the lily foliage. This can only be seen by cranking an exposure slider up to max.

lily_rawComp.jpg

 

 

Here are the R, G and B histograms for the entire photo. (The two green channels are averaged.) I truncated some of the data representation on the left because it was for the black background. We are interested here only in the flower data. The red histo shows primarily noise and deeply shadowed red leaf fluor, as mentioned.

lily_rawComp_histo.jpg

 

 

The raw composite can be exported from Raw Digger as a TIF for further processing. Add a little bit more light, contrast and detail enhancement and it makes for quite an acceptable rendition of the lily's fluorescence. Of course, not having actually seen the fluorescence, I can't judge just how bright to make the photo.

lily_rawCompPn.jpg

 

 


 

Here are exports of the red, green and blue channels from Raw Digger. The blue channel is the brightest (no surprise), followed by the green channel. There is not much captured in the red channel.

lily_chanBlue.jpg

lily_chanGreen.jpg

lily_chanRed.jpg

 


 

I wanted to examine some selected areas of the photo. First I looked at a central selection taken across the petals and stamens. The selected area is shown by the white rectangle.

lily_selection02.jpg

lily_selection_histo02.jpg

 

 

Next I looked at a selection made only on the stamens. The selection is shown by the white rectangle. There is no red fluorescence on those stamens. The fluorescence is a blue-green, more blue than green.

lily_stamen01.jpg

lily_stamen_histo01.jpg

 

 

Finally I made a tiny selection over one of the fluorescent fibers. This was just for fun. (We are all always lamenting the presence of those dang-rabbity fibers and dust specks!) They fluoresce blue with some green, but not enough green to really call it cyan. That is one way to determine whether the white balance of your UVIVF photo is correct -- check whether the fibers and dust specks are fluorescing a bright blue with a slight move towards green. The fiber fluorescence is very strong. You can see that the blue and green channels have hit the right-hand wall and begun to blow out.

lily_fluorFiber01.jpg

lily_fluorFiber_histo01.jpg

 


 

So, the reason for the blue cast in your UVIVF photographs is because you have used a Daylight (or possibly an Auto) white balance setting. It doesn't matter what converter is used. Here is an example using Photo Ninja with a Daylight white balance applied. It produces the same blue. (I couldn't spend too much time on this conversion. It is not at all as good as your original for sharpening, detail and contrast.)

lilypnDaylight.jpg

 

 

Is it possible in Photo Ninja to move the white balance setting away from all that blue? Of course. But moving the Temperature slider to the highest value 15000 does not fully relieve the blue misery. Still, this is a little bit more accurate version of the fluorescence.

lilypnTemp15000Tint-50.jpg

 

 

If I turn off all color correction in Photo Ninja for the NEF, then I get a conversion much truer to the raw composite. There are some variations in contrast and white/black point settings, but this version is basically the same as the edited version of the above raw composite. (3rd photo above, just after the first histogram.)

lilypnNoColorCorr.jpg

 


 

Where does the "color truth" lie for this fluorescent lily? Somewhere in between the raw composite version and the Temperature 15000 version. B)

 

 

THANK YOU for letting me play with your photograph! :)

 

 

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