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UltravioletPhotography

The Tree


Herman1705

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A lonesome tree in my flat country below sea level.

Sony A500 | Enna München Lithagon 28mm | Baader U 2" | ISO 200 | 1 s

 

post-132-0-99731100-1490974031.jpg

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I enjoy lone tree images.

The UV effect makes the image look like an old film image. Quite interesting, that effect.

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Andy Perrin

I was having trouble seeing what you meant, Mark, so I tried "turning it up to 11" with the saturation and then clicking white near the horizon. It looks to me like it might just be the clouds? Or possibly the fact that polarization of the sunshine changes with the angle above the horizon, which in turn interacts with dichroic coatings...

post-94-0-38184100-1491017043.jpg

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Given that the angle effect increases with wider lenses, would mounting such a filter at the rear of a lens - even a very wide angle lens - negate this effect?
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Andy Perrin
Um, I'm still not sure if this is even caused by the filter. It really looks like clouds to me. If it's the filter then I would think wider angle would be worse because the rays are coming in at steeper angles. Like trying to look at your LCD from way off to the side of the screen. (Not the same phenomenon but just to illustrate where the problem is.)
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Right; wider angle lenses exacerbate the effect (whether that is the case here or not). What I'm questioning is whether rear-mounting such a filter would avoid the problem of AOI dependent transmission. Pointedly, is light focused to a narrow enough angle by the time it traverses a lens to avoid any/most of the dichroic AOI dependence? If so, this would make an even stronger case to consider some kind of rear-mounting system (for my current lens).
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Andy Perrin
Oh, I notice it MUCH less with rear mounted filters. Yes, for sure it helps. It does not eliminate it, however.
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Is the tonal gradient in this image due to the filter having a dichroic coating?

It's a Baader U-filter.

 

If one likes to do some processing, this is the 'original' one (jpeg from raw):

post-132-0-72077900-1491060629.jpg

or can I put the RAW somewhere?

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To offer a raw photo, set up a free account on Dropbox.com. Upload your raw file to your Dropbox. Then create a shared link to post here (or in a PM or email).
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Thank you Herman. It is always enjoyable to work with other files than one's own. :) On Nikongear (Bjørn's site where I'm an Admin), we often have editing "contests". They've been very popular. It is always interesting to see how someone else interprets our work.

 

 

I converted the Tree in Photo Ninja and white-balanced on the road dirt. That brought out a dark false cyan in the plants and a very pale false yellow sky. The exposure was reduced by approximately 1 stop to bring the bright sky under control. Other tweaks were made to balance highlights & shadows, etc.

 

I then made differential contrasts in the sky with Capture NX2 to examine what was there. I think that the sky area on the lower left does contain some kind of fog bank or foggy cloud. I don't think I see any dichroic effect.

[update: Now I do - in the grass areas!!] There are more "normal" clouds in the upper right. The foggy area is scattering the light a lot, so in the final frame it appears a bit noisy. That's typical.

 

For fun, I also tried a couple of crops just to see how those might work out.

 

I could not locate my Sony supplied app for ARW files, so I might try again later when I restore that.

Hermann_pnPfResize.jpg

 

 

Here is an almost square crop. But it seems a bit unbalanced. Sometimes such an unbalance is used deliberately, for artistic tension I suppose. Does anyone know this photograph by Paul Strand? It has always stayed in my mind. http://www.mfa.org/c...ch-vermont-4683

Hermann_pnPf01.jpg

 

This pano crop was interesting to me. What does everyone else think???

Hermann_pnPf02.jpg

 

***

 

Thank you again, Herman, for permitting us to play with your photo.

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I forgot to add this (for the sake of any newbs, others ok to ignore).

 

When converting a UV photo with blown out areas - like the sky in this photo - the highlights are not always brought under control without a colour change. Some apps are better than others for controlling highlights. Capture NX2, for example, cannot always bring UV areas under control without inducing a cyan cast. Photo Ninja has been very very good at bringing highlights under control.

 

In the case of the foggy area (my assumption that was fog), there is the additional problem of scattered light from the fog droplets. So the foggy area in these conversions has a pale pink-ish tint not removed by white balancing. It could be removed by desaturating the red/magenta (whichever) colour in some app.

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In the last images I can see slightly different colors of the grass in edges compared to the center. I have observed the same effect using a clone of this lens (labeled: "Porst Super Weitwinkel 1:3.5/28mm") in combination with a Baader-U filter in front. I did not observe a similar effect with the Ennalyt 1:3.5/35mm.
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If I increase the color saturation I can see a circle with different color inside compared to outside. However in the inage with the tree it is now only visible in the grass.

In one of my own test images this circle is clearly visible.

 

post-147-0-61113700-1491168115.jpgpost-147-0-31924100-1491168136.jpg

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Andy Perrin
Yeah, now that is DEFINITELY related to dichroic filter/lens weirdness. It's like a less extreme version of what Andrea saw with that Edmund 340nm bandpass.
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Now I see the dichroicism in my edit!!! Funny, at first I did not. But when you showed the pushed saturation, I then immediately could find it in my edit. :D [We become somewhat "blind" to our own edits and often do not see things.]

 

But the area in the left lower sky still seems more like fog, which I don't see on the right?

 

Sure way to test for this kind of thing: Shoot straight up into an empty sky. Take care with the exposure so it does not blow out.

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Here are two done with ACR/PSCC

 

The first one without a camera profile (just using the RAW-Filter Option in PSCC several times on the image, and tweaking the contrast etc. a bit)

 

post-21-0-40481500-1491581125.jpg

 

 

The second one I opened the raw just with ACR and stored it as a DNG picture. This picture was then opened with the DNG_Profile Editor and there I created a special camera profile. Then I opened the RAW-file again with PS/ACR and just used this profile and a white balancing click on the gravel, maybe a slight adjustment on contrast and white /balck and dark areas and ready.

 

Both pictures saw a little sharpening by using the high pass filter when downsizing.

 

post-21-0-24121200-1491581149.jpg

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Andy Perrin
Everything has a strange glow here, especially along the horizon. Not sure I'm fond of the high pass filter.
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