Weird artifact when stopping down lens.

[ffureel]

Hi, here is a really rough test shoot. When the aperture is stopped down smaller I get an ever increasing bright spot in the centre of the image... Or a big vignette, whichever way you look at it. What is the cause of this? lens is stopped down in order of 2.8, 11, 22.

[Fotal]

I can only imagne that it's some kind of stray light perhaps caused by worn apeture blades?

[yalcinaydin]

I was also having the same artifact when doing reverse macro at f:16 with both Kiron 28/2 and Minolta 50/1.4, I guess it is light related stuff cause I got it most of the times but also not in some of my shots.

[peterqd]

ffureel, you don't say what lens this is. I had a similar problem with a Jupiter 21m 4/200 which I put down to internal reflections but I couldn't work out what was causing it as someone before me had stripped the screws trying to open the lens. Using a hood improved it a lot, have you tried one?

[Riku]

Isn't this just a dirty sensor? The spot on the center is dust and you can see other small particles of dirt too. It becomes more visible at small apertures.

[ffureel]

This lens was actually a volna 80mm pentacon 6 lens. Mounted to a 5d with a tilt adaptor, no tilt. I get it too with the flektogon 50mm pentacon 6 mounted on there too I have noticed today...

Either it is two lenses with something different with them, something inside the adaptor bouncing light, or just because I have odd lenses mounted on the wrong system.... I am not sure.

It is easy to Photoshop out I guess, would like to know what causes it though.

Does not happen on my standard 35mm mount lens.

[peterqd]