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Archive 2008 · Adapter for a 5D - Stop pin needed?

Cableaddict
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p.1 #1 · Adapter for a 5D - Stop pin needed?

I'm about to order some EOS lens adapters. These are for converting Rokkor 58's, so will be ground a bit & permanently attached to the lenses. Thus, the super-expensive types are a waste of money.

I was going to order some Hong Kong $5 specials, but a recently-read article stopped me cold. I read it quickly, very tired, and stupidly didn't save the url. It said that Eos adapters should ideally have a stop pin, and that without one, (here's where my memory gets fuzzy) it is possible for the lens to twist too far into the mount and cause damage. -But maybe I interpretted this wrong?

I thought stop pins were for setting infinity-focus, or alternately for tripping the aperture pin on M42 AF lenses, but this was something else. they definitely were warning of some kind of potential damage.

I'm looking at my Canon lenses, and don't see any such pin.

Does anyone understand what they were talking about?

Edited on Aug 08, 2008 at 05:22 AM

Aug 08, 2008 at 02:41 AM

Cableaddict
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p.1 #2 · Adapter for a 5D - Stop pin needed?

I just found that article again:

http://www.outbackphoto.com/the_bag/paul_adapter_note/essay.html

I was basically correct, except it's a stop SCREW, not a pin, and all my Canon lenses do indeed have it. (and so do yours.)

This seems like a fairly important thing. I'm kind of surprised that this hasn't been mentioned in any of the recent FM threads discussing adapters. What is not clear in the article is exactly WHAT part of the adapter would hit the camera's AF tab, causing the (potential) damage.

I suggest everyone read the article and post thoughts here.

Maybe Caldwell is wrong? Could the screw simply be there alignment of the red dots, or something?
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I have a CameraQuest CZ adapter coming, so no problem there. (the article says those DO have a set-screw.)

I have three of the "almost Kindai" adpaters coming for Nikon. Fingers crossed, but I think i see the screw in the photos.

I just ordered four cheapo m42 adapters to do the Rokkor 58 conversion. Oops. No set-screw that I can see. I wonder if one can modify them somehow?

-And why is it a screw, and not just a stop-pin? That implies adjustability, but there's no mention of this in the article. Are we supposed to adjust these screws when purchasing adapters that have them, or are they good to go as is?

Is this whole thing just silly, or is this really something to be concerned about?

Edited on Aug 08, 2008 at 06:35 AM

Aug 08, 2008 at 06:12 AM

cyberstudio
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p.1 #3 · Adapter for a 5D - Stop pin needed?

Every EOS mount must have a stop screw, or else you can twist the lens too far or backwards and cause damage to the camera body. However, the stop screw is not adjustable, and there is no need to adjust it.

It is not always a screw. Some manufacturers may choose to make one of the bayonets longer, and bend it downwards to achieve the same effect.

You look at the mount, and it is at 8 o'clock.

conurus

Aug 08, 2008 at 08:14 AM

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p.1 #4 · Adapter for a 5D - Stop pin needed?

In that article, Paul Caldwell states:

"My next step was to go back and closely examine all the lens adapters I currently had. These included:

1. Cameraquest, for both Nikkor and Contax
2. DSLReXchange for Contax
3. Zoerk/PSA adapter.

I noticed that of the three, only two were designed with some form of a stopping set device"

-And in the pics of the cheapo adapters I just ordered, I see no such screw.

Maybe you are correct. Maybe these adapters have some other way of stopping the movement, other than a set-screw, but are you 100% sure? Well, I guess it's a relatively easy thing to check, once they get here.

If they do it another way, is it possible that the "cheapo" way is less dependable? I'm thinking that if there really was a problem, someone would surely have posted by now about a broken AF tab. Still, it would be nice to be 100% sure before I start the conversions.

Edited on Aug 08, 2008 at 05:50 PM

Aug 08, 2008 at 09:02 AM


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