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

I had mentioned in my previous thread, 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 beam through it. The surprise came when I had it under my spectrometer, revealing its high and deep reaching UV transmission.  I have already shown that it performs quite well using the Baader-U filter, and here now its performance using some even deeper reaching UV filters, using a 340nm shortpass and the IDAS 330nm filter.

[click on image gets you a larger image]

VIS image using UV/IR Cut filter:
 

UV image using IDAS UV filter (approx. 330-370nm) at f5.6:
 

UV image using IDAS UV filter (approx. 330-370nm) at f8:
 

UV image using IDAS UV filter (approx. 330-370nm) at f11:
 

UV image using IDAS UV filter (approx. 330-370nm) at f16:
 

UV image using 340nm UV filter (approx. 320-340nm) at f5.6:
 

UV image using 340nm UV filter (approx. 320-340nm) at f8:
 

UV image using 340nm UV filter (approx. 320-340nm) at f11:
 

UV image using 340nm UV filter (approx. 320-340nm) at f16:
 

VIS and UV (IDAS) image side-by-side both at f8:
 

VIS and UV (340nm) image side-by-side both at f8:
 

As I had mentioned before, it got pretty clear that this lens has a very high UV performance, as at 365nm it transmits around 75%. Its peak transmission with Baader-U filter attached is around 68% at 360nm. At shorter wavelengths it still has a very useful 56% transmission at 340nm and 22% at  320nm.

Before I had shown here, that stopping down has improved sharpness significantly, especially in reflected UV light using the Baader-U filter. Now it gets quite obvious, that this lens is also performing very well at even shorter wavelengths, making it a very useful lens for reflected UV down to 330-340nm at an optimal f8/f11 setting, especially since the image size deviation between visible and UV image is also only 1.3% there .

I have written about that 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