Tuesday, February 1, 2011

Psychedelic Lilly - a surprising lens find for UV and VIS w/o focus shift

Well, while I was doing these "Psychedelic Lilly" test shots here and here with quite a few lenses (the winners being the Noflexar 3.5/35mm and the EL-Nikkor 5.6/80mm), I remembered having sitting around a box with some lenses made by a famous, but overlooked lens maker, I got a few years ago from a friend whom I used to do lens testing with. So I took the same setup I had in place with that nice "Stargazer Lilly" and also tested these lenses in visible light, but also in invisible UV. Prior to that I has already taken UV transmission tests, which turned out to be very promising, reaching down to about 320nm (-3EV) - see the following results.

[click on image to see a larger one]

These macro shots were done at f8, ISO400, 1/160s using Xenon flash, exposure adjusted using flash power control and ND filters. UV shots were done using the Baader-U filter. The shots further away were done at sunny winter daylight.
Here now a VIS-UV differential using the best of these lenses:

and yes, quite a nice sharp lens with quite good UV transmission and hardly any focus shift as the two overlaid images nearly perfectly match!

Additionally here the VIS shot:

Now the UV shot:

And finally the IR shot:

Now let's see how that very same lens performs for targets further away. Shots of the roof about 15 meters away on a sunny but cold winter day (ice reflects UV very well).

VIS-UV differential (UV is blue):

Which clearly shows, that also at that distance this lens has hardly any focus shift!
VIS shot:

UV shot:

And here now some quasi infinity shots. Target was that golden globe in the center of the image.

VIS left, right VIS-UV differential (UV is blue):

Here a comparison of VIS (left) and UV (right) in black/white:

Hardly any noticeable focus shift also at that distance! I had feared about a hotspot, but none was visible in my tests so far.
• hardly any UV - VIS focus shift in close up (macro), mid and far distance
• very sharp and contrasty in all tested ranges in UV and VIS
• no hotspot in any ranges in UV and VIS
• [also tested good for IR in close up (macro), but that was no prime interest]
Well, the surprise was a big one, as I also shot comparison shots using my UV-Nikkor and the difference was of course there, but that sharpness, contrast and nearly total lack of focus shift still amazes me, as this lens under test did beat both the Noflexar 3.5/35mm and the 5.6/80mm EL-Nikkor!
I have to research more on that lens, so more will follow on that one 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