Need help re Tominon 75/4.5 lens

[jjphoto]

I've just received a Tominon 75/4.5 lens which I suspect has been tampered with and reassembled incorrectly but I don't want to mess with it until I get a bit of advice.
Basically the problem is that centre sharpness DRAMATICALLY exceeds edge performance at all apertures and focusing distances. I don't know if any of this is normal with this lens. Any one else have one?

[ForenSeil]

At which magnification ratio are you using the the lens? It's made for polaroid macros only so bad corner performance is normal non-macro photos.

[kds315*]

[Alex H]

Check if the lens has been disassembled. I've gotten several lenses over past few years which were taken apart to clean and then assembled incorrectly. Most commonly enlarger and projector lenses. The inner negative double-concave element might be placed the wrong way.

[jjphoto]

Thanks all. I've since tried it at 'macro' magnifications and edge performance is certainly much better.

I think this lens could be very interesting to use for portraits due to it's aberrations combined with it's excellent centre sharpness.

JJ