On EL Nikkors for UV Photography and a Myth

So on technical aspect today. Lenses for UV photography are not easy to come by, are quite expensive ($.$$$ to $$.$$$) and quite a few people search months and years until they find a Nikon UV Nikkor 105mm, Pentax Ultra Achromatic Takumar 85mm or 300mm, Rodenstock UV Rodagon 60mm, Zeiss UV Planar 60mm of for the medium format photographer the Zeiss Hasselblad UV Sonnar 105mm just to mention a few and truely fully chromatically corrected (i.e. without focus shift UV-VIS). There are still two real UV lenses being manufactured, the Coastal Optics Micro Apo 105mm and the Tochigi Nikon UV 105mm. The interested reader might want to find more on those lenses (images, technical data etc.) on my parallel site http://www.macrolenses.de/objektive_sl.php?lang under the "special lens" section. (There are some 300 lenses listed in the macro lens
section, but that is another topic...)

So what's the alternative? Enlarger lenses come to mind and some are indeed not that bad. The older full metal type EL Nikkor 3.5/63mm is claimed to be the best for UV since its data sheet mentions that it may be used down to 350nm. So why not run a buch of similar types through my older spectrophotometer and see how they transmit UV? Ideally we would find a lens which
would transmit 300 - 400nm since that is the range a modern camera chip can resolve (like the Nikon D70 and D40 for instance, Canons don't do that at all) and also modern UV transmissive filters pass, like the Baader 2" U-filter.

Not really surprising the fact that indeed the 63mm does 350nm, but also others do quite the same; the 40mm being a real surprise, but due to the short focal length only useable for macro shots and not for infinity or landscape. But UV transmission is not all,
sharpness, contrast and flare (or the lack thereof) are quite important
aspects, too.

More on that technical part later. So here is the outcome of that test as a table (a click on it opens it in larger size). Cut-off wavelength is understood as the -3EV level compared to 100% transmission at 425nm (my subjective setting), so all these are relative values.




BUT be forewarned, all these EL-Nikkor lenses mentioned here, show substantial focus shift when used for UV photography, a fact which usually isn't mentioned but which makes working with them often a try-and-error game. Not really for the serious UV shooter, more a beginners lens to test the waters.

Now if you want an affordeable lens for shooting UV, I have developed a series of useful lenses with quite good UV transmittance and performance. I call them the X-lenses, the X135 being the most used one (f=135mm). A comparison with the UV Nikkor 105mm may be found here. Just do a search for X135 if you want to know more about that one or the X35 (f=35mm, a wide angle for UV) or X90.

Stay tuned on technical aspects, more will follow on that too...

More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos>