What is this?

[H3dfan]

A friend of mine is constantly having a blurred spot in all his images taken with my 35mm on my H3d1-31 camera. I swapped 35mm lenses before, shots are taken at F13 for reasonable DOF. The camera went back twice to Hasselblad but they assured him nothing is wrong. Does someone else have had the same experiance or does one have a solution?
The blurred spot is always exact in the center of the image.
Thanks for helping.

[NickT]

Maybe dirt on the rear element?
Nick-T

[H3dfan]

No, it happened with several 35mm lenses at F11 and more. It is always heftiest in the center of the image and looks somehow as if it is digitally softened and extremely sharpened after that. The camera and back went back twice to Hasselblad but they can notfind anything and state everything is as normal. Shots with other lenses do not show this defect so it must be a combination of back and lens.

[Dustbak]

I think this might be something. Take a close look at the MTF of the 35 at f8 and see how a sort of mushroom is developing compared to f3.5. The center is actually worse than than somewhat further in the frame. Admittedly a long shot, but it would explain the soft spot in the center and also why it is only appearing when closing down.