Doctor needed for diagnostic

[david o]

Hi,
here's an image I did this afternoon and there is a big green "worm" in the top middle of the stairs. This image is processed sharpened contrast but it also appear in the RAW... what could it be.
Thanks

[ericstaud]

Hi,
here's an image I did this afternoon and there is a big green "worm" in the top middle of the stairs. This image is processed sharpened contrast but it also appear in the RAW... what could it be.
Thanks
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My vote is for lens flare.

[Jonathan Wienke]

Definitely lens flare, if you look closely its shape exactly matches the patch of sky above the zig-zag piece of wall rotated 180 degrees.

[david o]

I see what you mean but I was in complete shadow... so no light could have hit the lens... Geez I feel dumb if you tel me that flare can appear even without direct light...

[Jonathan Wienke]

I see what you mean but I was in complete shadow... so no light could have hit the lens...

You did have light striking the lens, or you wouldn't have been able to capture an image. The light just wasn't coming from outside the frame. Look at the shape of the green blob, rotate it 180 degrees, and you'll see it matches the shape of that patch of sky pretty exactly.

[david o]

I just never had experience flare in such condition.
everyday is a chance to learn something.

[Dustbak]

It looks more to something I have experienced with some combinations of backs & glass. With some lenses I get a sort of purple hotspot in the center, with another lens it is a lighter hotspot with with a light ring.

My take, it is some form of reflection of the back element of the lens onto the sensor or IR-glass. It happens to me most often with images that have a form of backlighting. Some catalogue/packshots show this as well (white background becomes a form of backlighting).

Here the spot also appears to be dead-center. Watch whether this happens more often with the combination you have used. A solution is to shoot a custom white (LCC or Custom gain) first.

[david o]

It looks more to something I have experienced with some combinations of backs & glass. With some lenses I get a sort of purple hotspot in the center, with another lens it is a lighter hotspot with with a light ring.

My take, it is some form of reflection of the back element of the lens onto the sensor or IR-glass. It happens to me most often with images that have a form of backlighting. Some catalogue/packshots show this as well (white background becomes a form of backlighting).

Here the spot also appears to be dead-center. Watch whether this happens more often with the combination you have used. A solution is to shoot a custom white (LCC or Custom gain) first.
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I am not a strong technician and I buy your point. It doesn't look like a flare pattern to me.
And if sure the light must have it the lens to get the image to create flare it has to be a direct one... or am I missing something.

[Morgan_Moore]

I am sure it is a reflection of some sort

An internal reflection in the lense or camera body

no cure ? unless your camera/lens is filthy which I doubt

Attached image I have 'leveled' up the problem to make it extreme and fliped and transposed it onto the sky

It is the same shape

S

[david o]

man what you did to my image without my permission