Tuesday, January 11, 2011

Micro-Nikkor 105mm for UV photography?

Well, today have a look with me what the normal well known Micro-Nikkor f4/105mm lens transmits if used for reflected UV photography. I measured the transmission in my spectrometer without (rosé) and with Baader-U filter (pink line). Also shown is the comparison to using the "standard lens" for UV photography, the UV-Nikkor 105mm with Baader-U filter (purple line).

[click on image to see a larger one]

The Micro-Nikkor 105mm with Baader-U filter showed a transmission which was limited to the 354 - 393nm band with a peak at 375nm (about 18% or about - 2.5EV compared to using the UV-Nikkor).

So it obviously does pass some limited, but useful amounts of longer UV, but that would still be enough to show the typical UV flower patterns, as these show in the 370-420nm band from my experience. A normal exposure using an UV-Nikkor 105mm is around 2-4sec at ISO200 f8-11, so expect exposure times of 8-16sec or open up the aperture a bit more and/or raise ISO to 400.

Further you have to deal with focus shift that Micro-Nikkor has if used for UV, but that may be dealt with using my calibration technique, shown here on my BLOG.

In case you wonder what a camera sensor might be able to record and in which channels of that transmitted UV through lens and filter, have a look at this link here which shows the result of a scientific study a colleague of mine has conducted and published using a Nikon D80 camera (same sensor than the Nikon D200) which had its internal filter removed.

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