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José Martí Memorial in UV

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#1 Andy Broomé

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Posted 10 July 2018 - 03:32

During a recent day-trip to Havana, Cuba, I snapped a couple of UV shots around Revolution Square (I only had 20 mins to spare, so I didn't take any visible spectrum photos for comparison). Since I like to travel light, I only had my 18-55mm Nikkor kit lens with me.

Unfortunately, the image is quite noisy, as I had accidently left my camera on ISO800 from the previous evening.

Nikon D3200 full spectrum with Kolari Vision UV bandpass filter, 18-55mm kit lens @ 32mm, f/8, 1/15sec handheld, ISO800.

There's a clear tonal separation between the grey tower and white statue of Martí in the UV shot, versus white tower and white statue in the visible (plenty of visible spectrum photos in Google Images for comparison).

Attached Image: DSC_0463_RS.jpg

#2 Andrea B.

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Posted 10 July 2018 - 23:37

How did you get clouds in UV? ...oh wait....channel swap brings them out, yes?? :)

This is probably our first photo of a Cuban landmark! Nice to have.
Andrea G. Blum
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#3 Andy Broomé

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Posted 11 July 2018 - 02:28

View PostAndrea B., on 10 July 2018 - 23:37, said:

How did you get clouds in UV? ...oh wait....channel swap brings them out, yes?? :)
For the post-processing, all I did was lower the saturation of the purple and magenta tones (in Lightroom) then played with the temperature, luminance and dehaze to bring out the clouds. No channel-swapping.

I'm still wondering how/why I got a grey area in the sky around the tower. Perhaps it's a UV hotspot (I was shooting at f/8) but then again, I shot this tower off-centre, so I would expect the hotspot to be in the centre of the photo, not off to the left.

#4 Andrea B.

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Posted 11 July 2018 - 15:10

Thanks for the info about how you handle the clouds! They are frequently very difficult to bring out in a UV photo. I've sometimes been able to bring them out more by placing two NX2 color points on the lighest and darkest cloud areas and pulling the lights/darks further apart.

I understand some DXO app is now using color points, so I was thinking about trying a trial. I always liked those color points and have hung on far too long to my old Capture NX2.

I don't know what that grey area is. I don't think that this is a hotspot at all. Typically hotspots are, well, spots - like roundish pale haze - and like you said hotspots are pretty much centered. So I suspect that the artifact is some by-product of the particular processing you used. The halo-ing effect you have here can sometimes be caused by tone mapping or other extreme edits. And we often do apply rather extreme processing to our UV photos! BTW, I think the grey area is not "sensor bloom" because it is way too large for that aside from which the sensor manufacturers have eliminated all or almost all of it over the last few years.
Andrea G. Blum
Often found hanging out with flowers & bees.