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UltravioletPhotography

UV with a stock Nikon D500?


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The title says it all - a challenge we all know is impossible. Or is it?

 

The new Nikon D500 has these amazing capabilities of doing ultra high ISO captures. In fact, even at ISO 25600 to 51200, pretty good images can be attained and noise although present isn't that bad. Then one can go mad and push "ISO" up to some 1.6 Million, which is quite senseless and output is really poor.

 

Back in time, when I used my then new D2H, it did UV without modification. Or should I rephrase, "some kind of" UV as the images came out looking 'thin' and 'dull, but with indubitable UV features recorded.

 

Yesterday I had arranged an experiment in which I compared UV capability of mundane lenses such as various 50, 85, and 105 Nikkors, none of which famous for any UV performance. My reference lenses were the Coastal Optics 60 mm f/4 APO and the UV-Nikkor 105 mm f/4.5, both the reference in their respective focal length class. Camera was the Nikon D3200 with built-in Baader 'U' filter, the subject Marsh Marigold Caltha palustris, a species with know strong UV-dark patches in the flower, and all images were shot under sunny daylight conditions.

 

I used my D500 to capture reference shots in visible light and at the end of the experiment (very interesting results by the way, I'll make a post on that topic later), natural curiosity made me put a UV-Nikkor with external Baader 'U' filter on the D500.

 

Here is the result, f/11 at 13 sec, ISO 25600, using the UV-Nikkor,

 

D500 Caltha UV ISO 25600 T1606020107_v1BR.jpg

 

The image clearly shows in detail the intricate UV pattern of the Caltha flower. Like the D2H affair related to earlier, there was scarcely no 'UV colour' in the raw file, and I accordingly made it into black-and-white.

 

Although I won't swap my dedicated UV cameras for a D500, the result does underline the general truth that any optical system can record UV, given you push sufficient amount of UV through it, or equivalently, amplify the signal sufficiently.

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I've often quoted you on this. :D

That is, with a long enough exposure, UV light can be forced through most lenses and sometimes even the unconverted camera.

 

I had much poorer results when I tried this with my D810. Perhaps I didn't crank up the ISO enough?

 

Anyway, very interesting experiment for sure!

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Bandpass may be the issue, if you care about it. I recently tried a similar experiment with my A99V (which is my regular color workhorse.) I got images, but they had no chromaticity at all even when the converted camera showed plenty. I cannot say for certain whether the images were actually UV or just blue leakage; I would bet there was little or nothing below 380 nm in my case. I did not keep the images, so I cannot post them here. The "forcing" strategy can result in an image that is primarily out-of-band signal if one is not careful. OTOH, it was nice to have a viewfinder one could actually use...
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Andy Perrin
Yeah, this reminds me of the results I was getting with the CoolPix 995 (although the resolution is much better). I think it was a similar situation -- I was getting the 380-400 nm, which is enough to see some flower patterns, but no color.
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It is interesting that the colour, while false, seems meaningful to our* UV work as we have come to practice it in the last 5 years or so.

 

our* - I mean all of us here on UVP.

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As a yardstick, here is the D3200 with Baader U and the Coastal 60 mm f/4. Exposure here is f/11 at 1 sec, ISO 100. Slightly hazy sun in the late morning. Bandpass limitation in the optical system should not be an issue with the CO 60 lens (or even less with the UV-Nikkor 105).

 

UV D3200 ISO 100 T1606012983.jpg

 

The quality difference is obvious and the increased response to UV is of course massive with the modified camera and a UV specialised lens. However, as to the UV signature of the flower, basically the same conclusions can be drawn.

 

I shall later, when summing up the experiment, post the UV 105 Nikkor image as well. As the magnification of detail is higher because focal length is longer, pollen grains on the sepals are shown, which they are just barely visible here on the original full-size file acquired with the CO 60. In all other aspects, including the presence of iridescence, the CO 60 and UV 105 records are identical. Both lenses depict the dark patches as actually being 2-zoned and the iridescence is largely found on the slighly brighter, inner segment.

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It is interesting that the colour, while false, seems meaningful to our* UV work as we have come to practice it in the last 5 years or so.

 

I invoked it in this case because it can be an indicator of the proportion of shorter-wavelength information in the image, about which we are often curious. I actually have nothing against b&w.

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No, I don't either. Good B&W can be a superb vehicle for UV.

But when it comes down to it, I always seem to go with the false colour in UV.

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our* - I mean all of us here on UVP.

 

No need to generalize, Andrea. Personally, I see no sense in false colors in UV photography except for artistic/pictorial purpose.

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Arguments can be put either way.

 

As long as the false colours are reproducible and repeat for a given species, I for one like to include them. Converting to b/w means some information is lost. Had the colours been random, the case would be different.

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No need to generalize, Andrea.

 

??

I was attempting to be polite. Bjørn & I use UV false colour. So do most members. When I footnoted the English 'our', I wanted to make sure that readers understood it was not just Bjørn & I to whom I was referring with that 'our'. That would have been rude.

 

Standards of rudeness vary around the globe. English is a difficult language. Oh well.

 

*****

 

I am not yet ready to say that there is no valuable information in UV false colours (given the current state of the art in digital cameras).

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How about the idea that part of the UV false color we see when shooting with UV-only filters is UV induced visual fluorescence of the Bayer dyes?

Might as well toss that idea out and see if anyone has thoughts about that.

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