Olympus 50mm F1.2 Problem

[greenwell]

I have been given a very good condition OM 50mm F1.2 to try, I attached it to my OM4ti and started to take photos but there seemed to be something wrong with the camera, the shutter appeared to be sticking and when I took a sequence of photos the shutter got slower and slower until the viewfinder blacked out.
I put the lens onto another OM4 ti body and the same thing happened both bodies had fresh batteries and when I put other OM lenses on there is no problem.
I imagine that the mirror is catching something on the lens, the dealer who has loaned me the lens has closed for the weekend, I have found nothing on google.
All that I can think of is that maybe the lens was modified to fit another camera body but my untrained eye cannot see any difference.
Any ideas!

Regards

Rupert

[Liquid-Sky]

hi, have you check if the Iris isn't sticky? try to move the DOF with the button or at the back of the lens...

[greenwell]

Hi Liquid-Sky, thanks for your help, the iris does not move quite as freely as my other lenses, the lens is in very good condition but may not have been used for sometime.
I s there any way that I can improve the movement? I don't want to take it apart as it does not belong to me, I will have to return it to the dealer for him to fix.

Again very many thanks for your help.

Regards

Rupert

[John Hermanson]

You probably have oily diaphragm blades or at least oily coupling rings. Lens would need a complete degreasing (removal of all old separating helicoid ((focus)) grease), cleaning of all the tubes, blades and rings. This really involves taking the lens completely apart. John

[greenwell]

Thanks John, I will leave the lens for the dealer to sort out, we haven't discussed the price yet but it is a fine lens to focus, shame that I won't have any photos from it until it has been sorted.
Thanks again for your help.

Regards

Rupert