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Strange corners in images


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Please have a look at this photo. (Web prosessor on this site changed the colors in photo, so it was very difficult to see, I enclosed the image in a zip)

It is special taken to show what happens.
In upper right corner you can see a "shutter curtain"-like shaddow in 3 clair steps, the first from middle, is "brown" the two other is more purple looking.
You can se it in all other cornes as well, only diffrent caused buy the light and colors.

Picture is shot with Sony A7II

1/8 sek, F4.5, ISO 100, 24 mm

 

Lens: FE 24-70 F4 ZA OSS

Photo is shot RAW.

 

I have checked for same issue using Nikon D800, AF-S NIKKOR 24-70mm F/2.8 G ED and it not exist at all.

 

Does anyone have an idea about what cause this?

strange_corners.jpg.zip

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Guest Peter Kelly

This is a wild guess, but the only thing I can think of is some strange internal reflection. If so it may well be down to a combination of the lens and camera, but anyone's guess where the main fault lies!

 

When you do a mad basic push of exposure, the variations become more obvious and the only thing I can think of that might produce the angles in each of the steps are the different aperture blades.

Then it may be the different elements of the lens giving rise to the individual steps. I'm assuming that it may be a consequence of the shorter flange distance for the E mount, where your Nikon sensor will be much further away from the rear element.

 

There is an issue where older legacy lenses can suffer internal reflections in digital cameras that were never an issue with film, so perhaps this is something similar?

 

Unfortunately, I doubt there will be too many examples of brightly lit buildings against nighttime skies, so you may not hear too many others suffering similar effects. However, it might be possible to check my theory, to an extent, if you see how many blades there are in the FE24-70 and compare the angles. If they match those on the picture you may well have your culprit. I've no idea how to solve it or if there is a fix, I'm afraid.

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My guess is that it's actually vignetting from the lens. Pushing the file, in addition to the dark conditions, probably resulted in posterization of what should have been a "soft / progressive" shadow. I used to see this happening in the sky when I pushed files too hard with the Canon 5D mk II.

 

It might also contribute some kind of autocorrection from the lens profile, trying to "cancel" the vignetting.

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