I have this lens since quite a while but never really thought it would be useful for UV or IR due to its complex lens design incorporating lots of glass elements and a few cemented ones, based on the famous Biogon design of Dr Bertele. But well, I'm too much a curious engineer, so while I was digging through lenses, I thought, I should convert it and give it a chance...
Actually that lens design was developed and used long time as their (former GDR) best wide angle lens, used for their "Reihenmesskammer" for aerial reconnaissance. This lens here is a derivative of its larger brother, with an reduced image angle and most likely a symmetrical 8e/4g design.
Here is a technical article of my friend Marco Cavina, that covers such ultra wide angles nicely with lots of images and diagrams as well as showing never finished prototypes.
[click on image to see a larger one]
Focus shift? Very small and neglectable!
well, no complaints I would say..
[unfortunately also that flower has already started its decline, which UV shots reveal so easily...]
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