Friday, October 12, 2012

D.O. Industries 50mm old enlarger lens: reflected UV ultraviolet photography

I was digging through boxes, when some older, but new in box D.O. Industries f4.5/50mm enlarger lens fell into my hands. Well, I was curious to see how it would perform in UV, so I took a few shots in the Hermannshof park with it, using my "work horse" UV filter that never let me alone, the Baader-U filter. How nice that this lens has a 40.5mm  filter thread, as not all enlarger lenses have that. A simple short M42 focusing helicoid served as a focusing aid and as it has a Leica thread mount (M39), so simple M39-M42 ring was all needed to make it fit. All shots were done at f8 in evening last sunlight with not much UV left to use.

[click on image to see a larger one]

Rudbeckia hirta, wild form from Illinois:

same, but closer:

Rudbeckia fulgida:

Quite impressive performance for a most likely simple Cooke triplet 3e/3g lens. Oh and I forgot to mention, is has no (or barely any) focus shift. Here is its transmission graph versus my usual reference lenses, which reaveals how well this lens transmits UV:


More research and testing needs to be done, but it could form the basis of a comparably cheap UV photography system; we'll see...

Stay tuned, more will follow on that fascinating subject...

More info on this very interesting field may be found on my site