Nikon UV-Nikkor f4.5 105mm vs CERCO f4.3 94mm

As I was testing a Nikon UV-Nikkor f4.5 105mm, I thought it would be interesting to compare it to my CERCO f4.3 94mm workhorse lens, especially about possible chromatic aberration, sharpness and contrast. Target was a metallic precision ruler, light was sunlight. Only visible light photograhy was done here.

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CERCO top, Nikon bottom. Increasing f-stop setting towards the right, starting fully open leftmost.




Both lenses do not show CA. But interesting to note, how much higher the contrast of the UV Nikkor is. The CERCO shows futher decreasing contrast when stopping down (to the right) although flare control was used by using a deep hood against stray light. Both lenses are very sharp, but overall the Nikkor seems to be the clear winner here and it also covers FF sensors, which the CERCO does not do. Both are excellent lenses in terms of sharpness, but contrast and flare always need special attention, especially when using the CERCO multispectral lens.

I have compared quartz fluorite lenses in terms of their transmissions 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

Flare reduction and sunshade use in reflected UV ultraviolet photography

Today about flare redction when shooting reflected UV and the dedicated UV transmitting filters, like the Baader-U filter, my "work horse", for that. I'm using here my CERCO 94mm quartz fluorite lens, but in principle this method is applicable for any such lens. However, keep in mind, that quartz fluorite lenses for reflected UV are often single or even uncoated or show hotspotting, so it gets even more important to control flare efficiently, resulting in much higher image contrast and sometimes even removal of the hotspot. All images have been done at identical manual exposure settings, which were tested for correct exposure upfront.

Similar methods using such hoods have been used by others, I'm not claiming anything here, this just documents what I have done to further optimize my own setup.

[click on image to see a larger one]

Test images at nearly infinity (left to right) using (optimized for my camera's sensor size, other sensor sizes will require different sizes)

1) just the UV filter, no sunshade at all

2) a 40mm long sunshade with 50mm free diameter

3) a 50mm long sunshade with 21mm free diameter

The difference gets quite obvious, the longer and narrower the sunshade is, the better flare gets controlled.

Now some closeup shots, using the same method and sequence:

Also here shooting flowers at closeup, it gets pretty obvious, how much flare is present if using no or a simple sunshade, whereas a specilized deep and narrow sunshade results in much improved flare control, hence greatly improved image contrast.

Let me summarize:
Whenever shooting reflected UV (or other multispectral work), make sure to use the deepest and most narrow possible sunshade, that does not vignette, to achieve the best flare control and resulting in best possible image contrast. It is also suitable to control or even remove the effect of hotspots, some of those highly specialized lenses unfortunately show.

I have previously written about filter leakage 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