uneven solid white issue

[larc]

I few days ago I photographed some pencil drawings that were done on white paper. During post processing of the images I noticed a consistant unevenness of the large solid white area of the paper with some areas of the white being just slightly grayer than the others. Yesterday I did an experiment where took a photo of a bright white sheet of paper in very even sunlight and noticed the same thing.

Has anyone noticed any uneven exposure with solid white areas? This is important for me if I have more of this type of work to do.

Thanks
Larry

[imagepro]

I have noticed it only shooting with a flash on closeups of an all white subject....obviously the flash burst is hotter then the outer edges of the subject. Outdoors I have had no issues. Is the paper perfectly flat when shooting. If it is slightly bent or scewed it would account for the "graying" issue.

[larc]

I tried to make the paper as even lit as possible. It's not a problem on regular subjects or outside shots as it's just not noticible. It would also be understandable that unevenness would occur with a flash exposure, especially close up as you've mentioned.

I'll experiment more with it if it becomes more of an issue. I don't have do work with completely white backgrounds very often. Perhaps next time, when photographing pencil drawings, I'll also reset the tone to hard to beef up the contrast.


Larry

[MARK ASHER]

Hi Everyone,
I've noticed a similar problem when I've been shooting subjects on background papers. In my case there seems to be a cyan cast towards the top left-hand corner of the image. It seems fairly consistent from lighting set-up to lighting set-up, so doesn't suggest fringing from the light-boxes.
I think it may well be caused by the ultraviolet filter coating on the CCD chip being uneven.

I'm very busy at the moment, but I'll do a comparison test with my S1 in a controlled situation. Proper light/colour meter readings on a copy set-up in each corner to make sue every thing is even.

In the meantime if anyone has anything similar let me know.

Thanks, Mark Asher