XNUV - A new, much faster filter for reflected UV

kds315* · Expire: 2021-03-09

Today about a faster filter for reflected UV photography, as there seems to be demand for handheld UV shooting or shooting at higher speeds for instance for video work. After having thought about that for a while and about the whole chain light-object-filter-lens-sensor, an idea for a new filter came up, the XNUV, that I finally tested for the first time now using the Baader-U UV pass filter for comparison, a CERCO 94mm quartz flourite lens and my UV sensitive camera. Here presented in black and white diptych form, as the colors really don't matter for scientific work.

The used Rudbeckia hirta flower is reflecting from 320 - 420nm with a distinct peak around 365nm at its petal tips and creates a very distinct UV bullseye pattern and UV nectar guide for its pollinators and that serves nicely as test object here. Now on to the test results...

Ultraviolet (UV) image using Baader-U left) and XNUV filter (right):

Ultraviolet (UV) image using Baader-U left) and XNUV filter (right) - pattern detail:

Ultraviolet (UV) image using Baader-U left) and XNUV filter (right) - sharpness detail:

What is important to notice is, that the XNUV is also able to precisely reproduce this distinct UV pattern as well as it shows a quite improved sharpness as compared to the Baader-U filter. And most importantly it is repeatedly 3 stops faster than when using the Baader-U filter, which is a very impressive result as it will make it much easier also for video work.

I will report more about that filter here later, as more testing needs to be done. And no, it is not for sale, just for my own UV work.

[high resolution images are on my BLOG uvir.eu]

Hari · Expire: 2015-05-27

Wow! the difference is quite pronounced.

I don't know anything about UV photography but would using a red light source help in illumination?

kds315* · Expire: 2021-03-09

no Hari, it wouldn't as we talk about teh 300-400nm wavelength range here, red is from about 600nm onwards.

Hari · Expire: 2015-05-27

ForenSeil · Joined: 15 Apr 2011 Posts: 2726 Location: Kiel, Germany.

@Klaus
Wow! Difference is much bigger than I expected. Were did you find/order this filter and how much did it cost?

@Hari
Klaus blog is one of the best sources to start:
http://photographyoftheinvisibleworld.blogspot.de/

<400mm>~700nm is infrared.
Human eyes can see light from about 380nm (blacklight) to about 780nm (very red, look through an IR-filter!), depending on strength of the light and individual sensivity.

Bye the way I already have serious problems seeing anything through a 715nm filter. I can only see the sun while all my friends simply see a dark red picture of almost everything.

When we are talking about UV-photography we are usually talking about using the invisble light (invisible for humans, some insects are able to see UV (look at the "bee vision" in the blog), some reptiles like snakes are able to see pretty deep IR etc.) only between 200-380nm.
At around ~190nm air becomes intransparent, so there's a practical limit for UV-photography, as long as you don't shoot in vakuum or with an special artificial athmosphere.
Another problem of UV-Photography is that most lenses absorb a lot UV-light below 380nm. You need lenses which glas is made of calcium fluorite, quarz or similar. Only a few "normal" lenses are usable for UV-photography, like the medium format El-Nikkor enlarger lenses or the Novoflex 35/3.5 Macro for example.

At even smaller wavelengths the "light" (or radiation, whatever) becomes slowly able to go trough air again. At around 10nm, the light is even able to go through skin, flesh an bones. It's known as Xray(-photography) Smile

Of course you can also go into the opposite way, shooting even far above "normal" infrared. Some people are also doing photography with wavelengths of several cm- or meter, but due the long wavelengths the resolution is low and equipment is ultra large, so it's only useful for telescopes...

...there's so much to tell about light, much more than I could tell in one post Wink

Bye the way, I wonder if common DSLR's etc. are sensitive to Xray. A friend of mine has an Xray source, and I wonder I could make some interesting (and dangerous, kids don't do this at home, or at least not without a very long cable shutter) shots if I get an Xray lens somewhere.