8 replies to this topic

[9TE-5]

I have noticed an internal finely threaded part in a t-ring to eos adapter on the camera side.  It has a set screw through it. 

 

Is this threaded part just for internal anti-reflection or is it a real thread for, say, a small filter and the set screw locks it in?

 

My Sony adapter has a similar but smaller diameter threaded part and associated set screw.

 

Or does the screw head just limit the bayonet action into the camera?

Attached Thumbnails

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Edited by 9TE-5, 26 November 2022 - 09:21 AM.

[ngc7319_20]

Is this threaded part just for internal anti-reflection...

 

Or does the screw head just limit the bayonet action into the camera?

yes and yes

[emflocater]

yes and yes

So are you saying this screw acts as a stop? What limitation does the screw act for or prevent? I take that adjusting the screw up or down serves no purpose and that its use is just for the screw head to act as a stop, or does the screw head seat into some kind of slot that's on the bayonet side of the actual camera?

 

Cheers

Don

Edited by emflocater, 26 November 2022 - 11:23 AM.

[KLWalsh]

It’s not exactly clear in the photo, but I think the setscrew is used to set the exact 55 mm flange distance that is standard for DSLRs.
I have Nikons. On my adapters the section your arrow shows as ‘fine threads’ isn’t actually threaded, it’s fine grooves to minimize grazing reflections.

[9TE-5]

From what I can see with a loupe on my adapter, the groove comes to an end.  So it appears to be a thread, but not finely machined.  Possibly because its the easiest way to make a fine groove for anti-reflection.

 

Also, I checked where the screw head ends up on its journey into the bayonet and it does not seem to come to rest on anything.  That is done by the casting.

 

But if it were close to a filter thread it would be cool... and what is that screw really for, other than to lock something in place??  and surely they wouldn't depend on a loosen-able screw head to stop the bayonet, they would use a peg, or the casting which makes the most sense.

 

I was just curious if anyone else had discovered a use for this arrangement.

Edited by 9TE-5, 26 November 2022 - 01:18 PM.

[ngc7319_20]

So are you saying this screw acts as a stop? What limitation does the screw act for or prevent? I take that adjusting the screw up or down serves no purpose and that its use is just for the screw head to act as a stop, or does the screw head seat into some kind of slot that's on the bayonet side of the actual camera?

Yes, the screw acts as a rotational stop when a camera lens (adapter here) is inserted in the camera body and rotated.  My EOS lenses have the same stop -- sometimes it is a screw, and sometimes it is molded into the lens mount.  It is just a rotational stop and that is all.

 

When the lens hits the stop, a pin on the camera aligns with the slot (see pic), and the pin pops out and engages into the slot.  This pin locks the lens in place.  The stop ensures that the pin will align with the slot.  Otherwise the lens might turn too far and the pin would miss slot.

 

Edited by ngc7319_20, 26 November 2022 - 02:32 PM.

[emflocater]

Yes, the screw acts as a rotational stop when a camera lens (adapter here) is inserted in the camera body and rotated.  My EOS lenses have the same stop -- sometimes it is a screw, and sometimes it is molded into the lens mount.  It is just a rotational stop and that is all.

 

When the lens hits the stop, a pin on the camera aligns with the slot (see pic), and the pin pops out and engages into the slot.  This pin locks the lens in place.  The stop ensures that the pin will align with the slot.  Otherwise the lens might turn too far and the pin would miss slot.

 

SLOT.jpg

Awesome explanation!!

 

Cheers

Don

[9TE-5]

Well I stand corrected.

 

I removed my little screw (which was already loose) and, whilst holding the un-lock button down, the adapter was able to revolve further to the next bayonet key and come off again.  Not good to do with the electrical contacts installed, but this adapter didnt have that.   

 

The locating pin did engage by itself though but if one was in the habit of holding that down so as not to wear out one's expensive lenses it would not stop and possibly cause damage.

 

So it seems it is just a stop screw and the thread isnt really a thread - although it could be.

 

But I still wonder if something could screw into it.  (or something like a threaded reducing ring could epoxy into it and then be a mount for a filter.

 

Thank you all for your advice and I am smarter now than when I started.

[9TE-5]

and as a post script... the thread is left handed.  Ha!