vignietting again

[mentos_007]

I don't know if the post like this has already appeared here but if you were so kind to answer I'd be grateful
So I have a prob. with vignietting with my s5000 that appears whenever I use the fastest exposure time: 1/2000 sec. very simmilar thing happens with d70 of my friend also with short times. Is it normal or should we worry?? and if it's normal... so why?

 

[ksmattfish]

I don't know what kind of shutter the s5000 has, but if it's a leaf shutter you can get uneven exposure at very high shutter sppeds and wide apertures. A leaf shutter is an iris, like your aperture, that has to open all the way up. This means the center of the image actually gets more exposure. With slower shutter speeds the difference is so small you wouldn't notice, but with high shutter speeds the difference between the time of exposure for the edges vs the center can have a vignetting effect.

I believe the D70 has a focal plane shutter, so I don't know what's up there.