Tuesday, July 17, 2007

[UV] Rudbeckia - a study of lenses for UV photography

This was meant as a simple and unscientific comparison of some lenses for UV photography with focal lengths 50...60mm. All shots Nikon D70 + Baader 2" U-filter + Sb-140 flash @ ISO400, identical postprocessing for all results. Click on images to see larger files (1024 pix).

1) Rodenstock UV-Rodagon f5.6 60mm @f8 [this is the reference lens which has no no focus difference at all, works down to about 300nm, ideal for modern camera chips]:

2) Carl Zeiss Jena UV Objektiv f4 60mm @f8 [trial-and-error to focus, massive focus difference, that is why the image is that large, UV focus is much closer. Works down to 200nm]:

3) UV calibrated old german f2.8 50mm lens (still under development) @f8 [slight focus difference in usual i.e. closer direction, but very sharp and contrasty and useable down to 320nm]:

4) Carl Zeiss S-Planar f4 60mm @f8 [slight focus difference in unusual opposite direction i.e. further away. Quite a surprise that this 300lpm lens also does UV to about 340..350nm, the different color rendition shows the lack of UV transmission]:

5) Tomioka Macro Yashinon f2.8 60mm @f5.6 (due to limited and very narrowband UV response aperture had to be opened one stop) [slight focus difference in usual i.e. closer direction] [This is a non-working example of a modern multicoated lens; many others show the same UV transmission and blueish results; only useable to about 375..380nm which only leaves a useable 10..20nm window, this is why the image is nearly monochrome. Some tweaking might be applied to reach about the same color rendition as with the other lenses, but with substantial efforts] :

6) Steinheil Quarzobjektiv f1.8 50mm @f8 (about, since it uses that old pre WWII aperture setting of f7.7) [strong focus difference in usual i.e. closer direction] [This 1930ish lens is also a noncoated one, so it is sensitive to flare and doesn't have the high contrast modern lenses have...but still surprisingly good. The chance to also use it at f1.8 allows some dream like ethereal UV images. And it does it down to 200nm] :

7) selfmade lens from Quartz Achromat ca. 50mm @f8 (about) [strong focus difference in usual i.e. closer direction; strong abberation and bent field gets visible, but if that is all you have, not bad at all and useful down to 200nm, much more than modern camera chips can handle (ca 300nm)..] :

8 ) Rodagon f4 60mm @f8 [strong focus difference in unusual i.e. further direction. Not bad for an older enlarger lens, useful to about 350nm...]:

9) EL Nikkor f2.8 50mm @f8 [strong focus difference in usual i.e. closer direction. Also not bad at all for this older full metal style enlarger lens; useful to about 350nm...]:

10) D.O. Industries f4.5 50mm @f8 [strong focus difference in usual i.e. closer direction. Surpsingly good and contrasty for that cheap triplet lens; useful down to about 320nm]

This is the visual reference shot [also using the UV Rodagon 60mm]:

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