pentacon 70-210mm m42 problems

lexie · Joined: 09 Oct 2010 Posts: 14

i fitted the pentacon 70-210 i recieved this week to my sony a390 using the adaptor ring i bought with my helios 44m f2 but it is having problems.
it works well at times but at other times it sounds like the shutter is staying up too long and it shows the message "camera error". the helios still works well so i'm assuming it is to do with how the mount and the lens interact with each other, possibly with the inner piece of the lens assembly entering the camera too far.

will a new adaptor ring which is suited to the lens be needed to make work as it should?

if anyone has any experience with this type of problem i'd love to hear about it.

WolverineX · Posted: Sat Oct 16, 2010 9:41 pm Post subject:

post pix of the lens with adapter on. most likely some part of the lens protrudes too much and blocks movement of your mirror

lexie · Joined: 09 Oct 2010 Posts: 14

here are a couple of pics of the lens with adapter fitted. there seems to be a small protrusion of the inner part of the lens beyond the inner edge of the adapter.

the focal length always shows up as 50mm no matter what lens is attached to the adapter. i assume this is because it's matched to the helios it came with?
could this be causing the camera to give an error message?

Ash · Joined: 12 Mar 2010 Posts: 185 Location: Evanston, il, usa

I never heard that sony dslrs has ever had any mirror blocking problem with any lens. This would be the first one. Does your adapter has any electrical contact?

If no focal length information is supplied to camera from lens via electrical contacts then it fix your focal length to 50mm and aperture to 1.0

Could you post a pics of back of this lens with adapter attached when it is focused to infinity and when at MFD? That might give us a better view if the back will hit the mirror.

lexie · Joined: 09 Oct 2010 Posts: 14

fatdeeman · Joined: 13 Jun 2009 Posts: 780 Location: UK

lexie · Joined: 09 Oct 2010 Posts: 14

i've compared the pentacon to the helios and the helios lens protrudes further into the camera body than the pentacon. so i'm assuming that's not the problem

helios

could the rotating mechanism be sticking somewhere on it's movement between the lens and the adaptor?

pic of pentacon with adapter

i might just buy another adapter to see if it makes any difference, are there any af confirm adapters available for the a390?

i should add that the aperture controlling pin has been glued in both lenses.

lexie · Joined: 09 Oct 2010 Posts: 14

small update on this folks. i was comparing the screw threads on the m42 lenses i have and i noticed that the thread on the pentacon was very deep so i took a file to it in the hope that the little part on the camera which rotates when the mirror is lifted won't catch on it. there are scratch marks on it so i'm assuming that there is very little clearance for it to travel. i'll update later to report if there are any problems, but all seems good so far.