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A few more tests with AI-S Nikkor 24 mm f/2.8

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#1 enricosavazzi

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Posted 25 June 2020 - 11:20

While preparing a page for my site on the AI-S Nikkor 24 mm f/2.8 as used in UV imaging, I took a walk and shot some pictures, taking advantage of the mostly sunny summers on the island of Öland.

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A Viking stone circle (actually shaped like a ship or a corridor) a short walk away from our house. Rear mounted Baader U filter, custom white balancing. There is quite a hint of center flare as the sun was hitting the front element. I was using the Nikon HN-1 lens shade recommended for this lens, but obviously it is not enough.

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Perhaps I am digressing, but this is part of a map of archeological and historical findings around Borgholm, where I live. Some of them seem to be aligned along no-longer existing roads.

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A modern megalithic monument, a.k.a. a pond for collecting rainwater. Stella (foreground at the left) was not impressed. I performed an automatic white balance in Thumbs Plus, which this time gave a light-blue sky, somewhat odd for a UV image. Other times, even with the same picture, this automatic white balance gives unpredictably different results.

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This is an improvised picture of Stella and flowers, clearly showing the UV pattern of the flowers (Compositae but not Taraxacum). The image is however almost monochromatic. Still, better than average for a 24 mm full-frame lens.
-- Enrico Savazzi

#2 Andrea B.

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Posted 25 June 2020 - 17:04

Thanks for the results, Enrico. I'm quite fascinated with ancient stone circles, so I really liked the first photo.

This automatic white balance gives unpredictably different results.

I've also seen unpredictable results from auto white balance in various apps when applied to UV or multispectral files. I was thinking that an auto WB tool is probably tuned to look for near-gray or near-white areas and work off those. So a reflected UV photo might confuse such an app. :grin:

Stella with the flowers is a very cute photo.
(It's showing up slightly dark on my monitor.)
Andrea G. Blum
Often found hanging out with flowers & bees.

#3 enricosavazzi

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Posted 28 June 2020 - 09:42

My page on the AI-S Nikkor 24 mm f/2.8 is now online at http://savazzi.net/p...i-nikkor24.html
-- Enrico Savazzi

#4 enricosavazzi

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Posted 28 June 2020 - 10:06

View PostAndrea B., on 25 June 2020 - 17:04, said:

Stella with the flowers is a very cute photo.
(It's showing up slightly dark on my monitor.)
I agree that the flowers are dark. The reason is that most of the flowers were in the shadow of a fence, while Stella was in full sunlight. I tried first a zig-zag non-linear curve adjustment with weird results, so I just optimized for Stella in post-processing instead.
-- Enrico Savazzi