Tuesday, December 11, 2018

Baader-U Venus filter versus OPTOLONG Venus-U filter

Today about a new (to me) UV transmitting filter for reflected ultraviolet (UV) photography: the 2" OPTOLONG VENUS-U filter. This filter I have compared here with my work-horse UV filter, the 2" Baader-U Venus filter.

First it is about the resulting images and of course if there might be any IR leakage. The latter is quite important, as in early morning or late evening sunlight, where IR is predominant or when shooting against the sun or when reflective elements are present in an image,  IR leakage may lead to loss of contrast, or even obscuring the wanted UV details.

Now on to my tests which have been done using as a target an Oncostele orchid which has quite some prominent UV marks. Lens used was an UV-Nikkor 105mm, camera a modified Panasonic GH4, light a modified for high UV output Xenon studio flash. All shots were one at f8.

[click on image to see a larger one]

Baader-U filter (left) vs Optolong Venus filter (right:

Baader-U filter (left) vs Optolong Venus filter (right) - whitebalanced against gray BG:


It gets quite obvious that there is something going on here in terms of leakage, as the image shot with the Optolong Venus filter shows some blueish hint visible all over the orchid and also there is some central flare visible, wheras the Baader-U Venusfilter delivers a tack sharp and high contrast image. After whitebalacing against the gray background, which obviously was not possible with the Optolong filter, the result gets even worse, a rather muddy looking image results from the Optolong filter. In terms of exposure, the Baader U filter also has a slight 0.3 stop advantage over the Optolong filter.

Once I will have done some spectrometric transmission measuerements, I will certainly post those here later.

So please draw your own conclusions from this, if you would consider this a valuable filter for reflected UV photography. I will certainly continue to use my "work-horse" UV filter, the Baader-U.

I have written about IR leakage in filters for reflected UV photography 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

University of Zurich Zoological Museum exhibit «Insects - essential to life!»

The Zoological Museum of the University of Zurich, Switzerland has just opened the doors of a new special exhibit "Insects - essential to life!". It will be on display December 11, 2018 - June 30, 2019.

Included in this is a video with some of my best multispectral works, which my partner for this, animation artist Robin Noorda, has converted into a video presentation, named "Insecta Spectra".

Some insects (butterflies, Bees, ...) and also some animals (birds, fish, degus,..) are able to see ultraviolet (UV) light. Bees for instance can see Green and Blue and UV, but no RED, but butterflies and birds can see Red, Green and Blue and UV, so both can see what we humans cannot see - UV. To make that visible for us humans, I developed a special filtering and optical mapping method, which allows to simulate, how we would see the world, if we had such special UV receptive eyes.

Have a look at the preview video clip [click]:

Certainly and exhibit worth visiting with the whole family!

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