Surprising STEINHEIL f2.8/50mm lens for reflected UV photography II

I had previously mentioned that a few years ago I got an older lens, which was made decades ago by famous lens maker STEINHEIL. It is a possibly single coated, well made 2.8/50mm lens which attracted me, since it showed some seemingly good UV transmission when shining an 365nm UV LED through it. The surprise came when I had it in my spectrometer, revealing its high and deep reaching UV transmission, no other normal lens so far showed. Now some outdoor images taken with it, all at f2.8 to see if that lens speed could be used. Light was overcast sunlight.

[click on image gets you a larger image]

VIS image using UV/IR Cut filter:
 

UV image using Baader-U filter (approx. 320-395nm):
 

UV image using Baader-U filter (approx. 320-395nm) and 340nm shortpass filter stacked:
 

VIS image using UV/IR Cut filter:
 

UV image using Baader-U filter (approx. 320-395nm):
 

UV image using Baader-U filter (approx. 320-395nm) and 340nm shortpass filter stacked:
 

It got pretty clear that this lens has a very high UV performance, at 365nm it transmits around 75%, very close to the Kuribayashi 35mm which has 80%. Its peak transmission with Baader-U filter attached is around 68% at 360nm. Using that deeper 290-340nm UV filter which peaks at 334nm with 68% transmissing, it still has a 32% total transmission at its peak at 338nm.

At f2.8 however the resulting images do not look as sharp as wished for, so another test will have to reveal if stopping down will improve sharpness considerably.

I have written about this lens more HERE.

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

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