Lens adapters - Should they "lock"?

leroilightning · 10-28-2017, 07:13 PM

I bought some vintage lenses and adapters to mount them to my NEX-5T.

QUESTION: Should the lens "lock on" to the adapter? For example, I have an MD-to-NEX adapter where the lenses go on with a slight turn but if I keep rotating the lens or turn the focus ring too strongly the lens just about unscrews from the adapter. (Not a problem for M42-mount adapters because lenses literally screw fully on.)

Is this normal?

Adam · 10-28-2017, 07:25 PM

For bayonet lenses, I'd expect them to lock. Would depend on the specific adapter supporting it, though, as there's a tab in the mount that needs to engage.

leroilightning · 10-28-2017, 07:25 PM

Forgot to say: is this also normal for the K/PK-mount (which looks similar to the MD mount)?

leroilightning · 10-28-2017, 07:29 PM

Thanks Adam. I'll look more into that. My adapter has a little button thing but it doesn't seem to lock the lens in place, unless I'm doing it wrong.

Adam · 10-28-2017, 07:41 PM

Sounds like you might be using the wrong adapter, as the K mount is not identical to other mounts. Could you post some pics?

**UncleVanya** · 10-28-2017, 08:37 PM

My K to M43, FD to M43 adapters all lock. My Samsung NX system adapters all were similar when I had it. My buddy has a Sony NEX system with adapters for a dozen lenses without problems like you describe.

Jonathan Mac · 10-28-2017, 11:43 PM

If the lens locks onto a native camera body then it should lock onto an adapter. I have a Minolta SR adapter to use with my Fujifilm X-M1 and all the Minolta lenses lock into place, as they do with the K-mount ones when using the K adapter.

I have an M42 to EOS mount adapter to use with my EOS film cameras and that did not originally lock onto the camera body because the hole in it was too small for the locking pin on the mount. The solution was to drill the hole a bit larger and now it works fine. You may have a similar issue with your adapter - check the locking pin on the adapter and see if it is too large or misplaced relative to the hole.

Not a Number · 10-29-2017, 02:14 AM

If the adapter has a release button or lever on it then the lens should lock into place. However it is possible to go beyond the locking position with some adapters. These lack the stops in the mount to prevent the lens from being turned beyond a certain point. It is possible the locking mechanism is out of adjustment, alignment or tolerance. For instance I have two adapters for Minolta SR lenses to K-mount bodies. One of the adapters I had to press the release button in order to even begin to turn the lens in the mount. The screw holding in the locking arm was loose and I just needed to tighten the screw.

The majority of bayonet mounts look similar in that they have three tabs or ears. The sizes of the tabs vary from mount to mount and in most cases are incompatible. The position of the locking slots varies from brand to brand also. As do the flange to sensor/film/image plane. The early Nikon bayonets will fit on Pentax K mounts but the position of the locking slot differ by 180° and the flange distances are not the same. It is possible that some adapters are so outside the specifications for the mount they are supposedly made for that other mounts may fit in them.

The locking mechanism between Minolta SR and Pentax K mount are not compatible. On the Minolta the slot is on one of the bayonet tabs. On Pentax K mount the slot is on the mount base.

**BigMackCam** · 10-29-2017, 02:54 AM

Originally posted by Not a Number

If the adapter has a release button or lever on it then the lens should lock into place. However it is possible to go beyond the locking position with some adapters. These lack the stops in the mount to prevent the lens from being turned beyond a certain point. It is possible the locking mechanism is out of adjustment, alignment or tolerance.

This is quite common with some of the lower price / lower quality adapters. There can be quite a lot of "play" in the locking pin, such that it doesn't align with the hole on the lens mount - and sometimes, they're just machined inaccurately.

For cheaper yet still decent quality adapters, I've been very happy with "Pixco" and "K&F Concepts". They're well-finished and seem to be machined to quite close tolerances...

**jlstrawman** · 10-29-2017, 09:20 AM - **1 Like**

Fotodiox Pro adapters, are a bit more expensive, but made to better toleranances and work very well where others have not.

leroilightning · 10-30-2017, 12:24 AM - **1 Like**

Thanks guys! That info really helped. I checked the MD-NEX adapter I have: it has a tiny metallic nub on the inner ring (attached to a thin protruding button on the outside ring of the adapter). So I visually looked to see where it SHOULD lock and rotated the lens to that position, then pressed the lock switch to help let it click into place. Now the lens is locked in and won't move. Nice! (Before, the lens was rotating past the lock position because the nub was not clicking into place on its own.)

10-28-2017, 07:13 PM	#1
leroilightning New Member Join Date: Oct 2017 Posts: 4	Lens adapters - Should they "lock"? I bought some vintage lenses and adapters to mount them to my NEX-5T. QUESTION: Should the lens "lock on" to the adapter? For example, I have an MD-to-NEX adapter where the lenses go on with a slight turn but if I keep rotating the lens or turn the focus ring too strongly the lens just about unscrews from the adapter. (Not a problem for M42-mount adapters because lenses literally screw fully on.) Is this normal?

10-28-2017, 07:25 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	For bayonet lenses, I'd expect them to lock. Would depend on the specific adapter supporting it, though, as there's a tab in the mount that needs to engage. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

10-28-2017, 07:41 PM	#5
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	Sounds like you might be using the wrong adapter, as the K mount is not identical to other mounts. Could you post some pics? Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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10-28-2017, 07:29 PM	#4
leroilightning New Member Join Date: Oct 2017 Posts: 4 Original Poster	Thanks Adam. I'll look more into that. My adapter has a little button thing but it doesn't seem to lock the lens in place, unless I'm doing it wrong.

10-28-2017, 08:37 PM	#6
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,407	My K to M43, FD to M43 adapters all lock. My Samsung NX system adapters all were similar when I had it. My buddy has a Sony NEX system with adapters for a dozen lenses without problems like you describe.

10-28-2017, 11:43 PM	#7
Jonathan Mac Pentaxian Join Date: Apr 2009 Location: Madrid, Spain Posts: 10,897	If the lens locks onto a native camera body then it should lock onto an adapter. I have a Minolta SR adapter to use with my Fujifilm X-M1 and all the Minolta lenses lock into place, as they do with the K-mount ones when using the K adapter. I have an M42 to EOS mount adapter to use with my EOS film cameras and that did not originally lock onto the camera body because the hole in it was too small for the locking pin on the mount. The solution was to drill the hole a bit larger and now it works fine. You may have a similar issue with your adapter - check the locking pin on the adapter and see if it is too large or misplaced relative to the hole.

10-29-2017, 02:14 AM	#8
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	If the adapter has a release button or lever on it then the lens should lock into place. However it is possible to go beyond the locking position with some adapters. These lack the stops in the mount to prevent the lens from being turned beyond a certain point. It is possible the locking mechanism is out of adjustment, alignment or tolerance. For instance I have two adapters for Minolta SR lenses to K-mount bodies. One of the adapters I had to press the release button in order to even begin to turn the lens in the mount. The screw holding in the locking arm was loose and I just needed to tighten the screw. The majority of bayonet mounts look similar in that they have three tabs or ears. The sizes of the tabs vary from mount to mount and in most cases are incompatible. The position of the locking slots varies from brand to brand also. As do the flange to sensor/film/image plane. The early Nikon bayonets will fit on Pentax K mounts but the position of the locking slot differ by 180° and the flange distances are not the same. It is possible that some adapters are so outside the specifications for the mount they are supposedly made for that other mounts may fit in them. The locking mechanism between Minolta SR and Pentax K mount are not compatible. On the Minolta the slot is on one of the bayonet tabs. On Pentax K mount the slot is on the mount base.

10-29-2017, 02:54 AM	#9
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,674	Originally posted by Not a Number If the adapter has a release button or lever on it then the lens should lock into place. However it is possible to go beyond the locking position with some adapters. These lack the stops in the mount to prevent the lens from being turned beyond a certain point. It is possible the locking mechanism is out of adjustment, alignment or tolerance. This is quite common with some of the lower price / lower quality adapters. There can be quite a lot of "play" in the locking pin, such that it doesn't align with the hole on the lens mount - and sometimes, they're just machined inaccurately. For cheaper yet still decent quality adapters, I've been very happy with "Pixco" and "K&F Concepts". They're well-finished and seem to be machined to quite close tolerances...

10-29-2017, 09:20 AM - 1 Like	#10
jlstrawman Site Supporter Join Date: Feb 2010 Location: Midwest US Photos: Gallery Posts: 1,058	Fotodiox Pro adapters, are a bit more expensive, but made to better toleranances and work very well where others have not.

10-30-2017, 12:24 AM - 1 Like	#11
leroilightning New Member Join Date: Oct 2017 Posts: 4 Original Poster	Thanks guys! That info really helped. I checked the MD-NEX adapter I have: it has a tiny metallic nub on the inner ring (attached to a thin protruding button on the outside ring of the adapter). So I visually looked to see where it SHOULD lock and rotated the lens to that position, then pressed the lock switch to help let it click into place. Now the lens is locked in and won't move. Nice! (Before, the lens was rotating past the lock position because the nub was not clicking into place on its own.)