Are there risks in using an adapter ring?

Question

I have found a couple of old Zenit lenses in a drawer. I have found online, for a very cheap amount (about 10 eur) an adapter ring (from M42 to EOS mount).

The lenses have not been particularly well preserved in the years, so I don't expect to have found a treasure, but given the very small amount of money involved I could give it a go.

The question is: will I be risking anything using this adapter? Is there some specific thing to avoid or to do? If there is even a small chance of - who knows - damaging/bumping/touching something on the camera (specifically I have a 50D), I don't think that it would be worth it.

If on the the other hand the worse which can happen is that the lens turns out to be not really usable or that focus at infinity is unattainable, I will try it.

Answer 1

There are two possible issues with adapters:

• A cheap adapter may not be machined to a high standard and be outside acceptable tolerances. This could affect focusing, or even damage the mount, though this is unlikely. Screw mounts may be slightly to big or small, and lenses could get stuck in them if the metal binds.
• Some lenses may collapse behind the mount and could collide with and damage the mirror (or sensor for a mirrorless camera). Examples of this would be old collapsible Leica lenses, or some old wide angle lenses.

Either way you simply need to be careful, inspect the adapter carefully, mount by itself and check that it is held firmly in place and that there is no give. Ensure it can be easily removed before mounting the lens. Inspect the lens and check that it does not protrude to far back, check at different focal lengths and zoom distances. Connect the lens to the adapter while not attached to the camera and ensure it can easily be removed. It would be wise to clean the mount on the old lens as well.

Chances are you will have no problem but care should always be taken when using non standard equipment.

Answer 2

I have 3 lenses with M42 mount that I use on my Pentax dSLR. I've especially grown fond of Zenit standard lens (Helios 44-2, 58mm f/2) for its relatively short minimum focusing distance, fast preset-style aperture and portraiture focal length (on APS-C). I have had no problems using them with an adapter.

When I researched using M42 on a dSLR, two possible problems were mentioned:

• An adapter (especially a cheap one) might get stuck in your lens mount when the little tab holding it in place bends in an unfavorable way, seems to be a problem specific to Pentax and can be prevented by screwing off the tab (the adapter will now not lock in lens mount, so the lens will have to be handled more carefully).
• Some lenses have rear elements or aperture stop-down pins protruding past the screw-mount; if they extend too far, they might collide with mirror. This risk of collision is higher with full-frame cameras thanks to their larger mirrors. Slight extension is okay - due to Canon's shorter flange focal distance the adapter already keeps the lens 1.5mm further away from focusing plane than it would be on the body it was designed for. My wide-angle lens from Zenit, Mir-1B (37mm f/2.8), has its element extended by about 6mm in infinity focus. Works on my Pentax, but is reported to clash with mirror on a Canon 5d. However, the EF-S mount used on APS-C Canons is specifically designed to allow back elements of lenses to be closer to sensor.