Re: UV colour photography

[NFOTO Bjorn Rorslett <nikon@xxxxxxx>]

Several people have suggested I should share some of my experiences with UV
colour photography to a wider audience. Eventually, I would like to present
some of the images on my (hopefully) forthcoming web site. As of now my UV
images have been published only in Norwegian nature photography journals.

I use mostly 35mm gear for my UV photography and to this end, the
UV-Micro-Nikkor 105 mm f/4.5 is my favorite lens. It is extremely sharp and
sharpness is enhanced by using it for UV photography (shorter wavelengths
inherently give higher sharpness). For UV photography, I add the Nikon
equivalent to a Wratten 18A filter. This filter is mounted in a hinged frame
and can be swung to the side for focusing. The UV-Nikkor is designed with
quartz and fluorite lens elements and has no focus shift from visible to UV,
a feature that is very valuable in practice. It transmits in the range
220-900 nm and thus can be used both for UV and IR work. I use only Fuji RTP
film, this is a tungsten film that is the best choice for UV colour work
according to my calibration experiments. For UV flower photography, I often
use the Nikon flash unit SB-140 which is designed for UV and IR photography.

I have tested a large number of lenses to find those suitable for UV work.
Unfortunately, they are few. Modern coatings and glasses transmit very
little UV so as to make newer lenses impractical for UV photography. In the
Nikon line, I have used GN-Nikkor 45mm f/2.8 (for F-series camera), and some
vintage Nikon S-series rangefinder lenses (21mm f/4, 35mm f/2.5) besides the
UV-Nikkor 105. I have also had good results with a microcopying lens, Zeiss
Ortho-S-Planar 60mm f/4, which I salvaged from a rubbish heap.

Pinhole photography is entirely possible in the UV-region and again Fuji RTP
should be pressed into service. I have tried this on 120 film and plan to
use 4x5" sheet film this summer. A current project is trying UV-pinhole
photography in my underwater housing for the F3.

When I first began experimenting with UV photography in colur, I erroneously
thought I would get only bluish images. Practice has shown that one obtains
a very specialised colour palette consisting of blue, bluegreen, white,
grey, black, magenta, light yellow, deep purple and red hues. This colour
rendition results because the UV-transparent filters have small secondary
lobes in their transmittance spectra to transmit small amounts of violet and
deep red. However, the colour film, being low in sensitivity to true UV,
will pick up the additional radiation during the long exposure and blend
them with the UV-generated image. This makes for fascinating colour patterns
of flowers, for example. One of my favorite subjects is the dandelion which
exhibits dramatic floral UV patterns. Wave patterns also make for good UV
images.

regards from wintery Norway/bjorn


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