M42 adapter and Pentacon 1.8 compatibility issue, Sony Alpha

[Adi06]

Hello everyone,
I need help with an m42 to sony alpha adapter (chipped) which I'm using with a Pentacon Electric 50mm 1.8. The problem is that the lens doesn't fit all the way into the adapter as shown in pictures below. It is off by 2-3mm so I have an extension tube effect and can't focus to infinity.

I'm very new to manual lenses so I don't really know if this problem is due to the adapter or this particular lens. Can anyone help me out?

Thanks in advance,
Adrian

[eddieitman]

[TrueLoveOne]

Does your adapter do this with other M42 lenses too? Or is it just this one?

I have several Pentacon lenses, and many other. I use a simple non-af-confirm adapter, and all of my lenses can focus to infinity and they all screw in "to the end".
I am also a Sony user.... all works just fine!

If the contacts on the back of the lens are the problem... you could remove them, as they are of no use to you anyway. But they should retract when screwed on a camera or adapter, there are springs underneath them.

The thread on your adapter or on your lens is not okay if you ask me....

[SinfulSaint]

That's a bad adapter I'd say.

Be advised that Pentacon 50/1.8 when mounted on M42 adapter can not achieve infinity focus at f2 (it can, but stays very soft).

I had to shave off some .25 mm off of my adapter to get a sharp picture at f2.

Same works for all of my M42 lenses. Pentacon 29, Helios 44M-4, 44-2 and others.

So far I've tried 3 different ebay adapters. Even big_is ones.

Sony A33 user.

[peterqd]

Yes to Martin about removing the contacts. If you look at a Praktica camera this lens was designed for, the "track" which the contacts touch is recessed slightly. This allows the mount faces to come together as they should. The adapter you're using does not have this recess. This sounds the most likely reason for your problem.

Another possibility that affects fast lenses with large rear elements is that the hole in the pin flange (the lip that depresses the auto aperture pin) is too small and the rear element jams in it. I had this problem with the Takumar 1.4/50. You can test this by turning the lens to the minimum focus distance before mounting and the lens should screw in fully. I think this is less likely with your 1.8 lens, although member NewStuff did report yeserday that he couldn't mount a Pentacon 1.8/50 on his new NEX adapter.

You don't need the electrical contacts unless you're using a Praktica camera, so they can be removed with no loss of function. You also don't really need the pin flange as this lens will stop down using the Auto/Manual switch. If the flange is the problem, you might be able to remove it altogether if you take out the threaded shiny part of the adapter. There are usually three small pointed clamping screws. Make sure when you re-assemble that the screw points relocate back into the original positions.