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m42 adapter modification

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Bob J View Drop Down
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Post Options Post Options   Quote Bob J Quote  Post ReplyReply Direct Link To This Post Posted: 23 January 2007 at 18:58
I'd say not to worry about the lip at A - the critical thing is to take metal off the face of the adapter (which comes into contact with the end of the lens) - it is this that needs to be reduced.

If you have a vernier caliper you can measure through the hole in the fact of the adapter with it in place - the difference between the face of the adapter and the Minolta lens mount underneath should be about 0.9mm.

Bob
 



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Post Options Post Options   Quote rjmccutchan Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2007 at 05:23
I sanded "A" flush with the flange and that seems to do the trick! The object that I took a shot of was approx 150 yards away and it was in focus.

Thanks!!
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Bob J View Drop Down
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Post Options Post Options   Quote Bob J Quote  Post ReplyReply Direct Link To This Post Posted: 07 February 2007 at 19:26
By way of showing how to measure the gap between the adapter face and the camera face, here are a couple of pics that may help:


Position the adapter so that it is just off latching - this way you get a clear way through the hole to measure...


The depth probe of a vernier caliper can then be used to measure the distance between the camera's flange and the one of the adapter - the MAF film to flange distance is 44.5 while the one for M42 should be 45.46, so the gap should be 0.96mm (or less).


Here you can see that my adapter is now slightly too short, so my M42 lenses will focus beyond infinity - but that is preferable to not quite getting there!

I ended up taking about 0.25mm off the face of my adapter - the pitch of the thread for M42 is 1mm per revolution, so the index marks, which were originally on top, are now in line with the lens release button.

I found checking how far a lens went beyond the top point an easier way of checking how much I had taken off the adapter while taking it down - ie just refitting the lens to the adapter, rather than having to clean the adapter up, put it back on the camera and re-measure.

Bob
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Post Options Post Options   Quote pepcok Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2007 at 01:23
Nur,
I finally modified my adapter according to your suggestion.. and it's great. Finally my takumar focuses to infinity.. :) thank you.
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Post Options Post Options   Quote Arkku Quote  Post ReplyReply Direct Link To This Post Posted: 20 March 2007 at 16:03
I tested all four of my M42 adapters today. Three of the adapters were clearly off and a Kood-branded one appeared to be exactly right. However, after I sanded one of the initially incorrect adapters down a bit, it actually got ever-so-slightly better than the Kood one.

I didn't measure the thickness of the adapter, but rather photographed a building at infinity while placing a tree almost-but-not-quite at infinity in front of it. Whenever the tree was better in focus than the building, I knew the adapter was still too thick. The last fractions of a millimetre came down to eyeing minute differences in the building, however, after the adapter was slim enough not to focus on the tree but still not perfectly focused on the building either.

Here's a comparison between the initially best (Kood) adapter and the worst (unbranded black adapter from the Zenitar fish-eye):



Though this scaled-down version of the image is small, the bricks on the "bad" adapter on the left appear clearly softer. I repeated the test for all my adapters a couple of times with different lenses to be sure it is not just me or the lens.
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Post Options Post Options   Quote Dorset Mike Quote  Post ReplyReply Direct Link To This Post Posted: 18 May 2007 at 12:39
Instead of sanding can a lathe be used to turn the requisite amount from the face?
Cheers MIKE,



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Franc View Drop Down
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Post Options Post Options   Quote Franc Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2007 at 01:31
Greetings.
Hi Dorset Mike. Used to live there myself, many years ago. I have just been reading through this thread with interest.Your comment about using a lathe to shave off the face of an adapter should be fine as long as you take great care in mounting the adapter in the chuck to avoid crushing the thing.And ensure you mount it so as to shave the face evenly. My problem is that when I mount my adapter to my Dynax 7xi or a Sony alpha I get the message that there is "no lens attached" and cannot operate the shutter. There is no interference between adapter and camera contacts. So what stupid thing am I doing here. Any clues anybody. Love to hear from you.
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Post Options Post Options   Quote keesey Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2007 at 03:20
To get the lens to work on the alpha you will need to go into the menu go across and select the tab on the right that looks like a cog and then you need the second screen of this menu and change the shutter lock from "on:no lens" to "off:no lens" and then you will be able to take pictures

Mark
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Post Options Post Options   Quote Quietman Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2007 at 04:08
Dorset Mike,
A lathe can do a beautiful job. My father-in-law used his to shave > .25mm off the front face of my adapter. It did a wonderful job but he was quite concerned about crushing the piece while he was working on it. It took multiple attempts to remove enough material for my 50mm Takumar to reach infinity. I've been using the adapter for several months now and am absolutely thrilled with the results.

... Quietman



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Franc View Drop Down
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Post Options Post Options   Quote Franc Quote  Post ReplyReply Direct Link To This Post Posted: 21 May 2007 at 00:59
Mark,
Thanks for that. That'll teach me to read the manual thoroughly!!
All now working as it should do.

Edited by Franc - 21 May 2007 at 01:05
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Post Options Post Options   Quote vk4tnt Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2007 at 13:04
Yes, a lathe can do wonders, but if you are unlucky like I was once with an adapter it can warp the flange because of the thin material
Science is like sex:
sometimes something useful comes out, but that is not the reason we are doing it.

—Richard Feynman
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Post Options Post Options   Quote polyglot Quote  Post ReplyReply Direct Link To This Post Posted: 04 December 2007 at 09:32
A different take on this - I have an adapter I bought from a HK eBay dealer (lai0486), it has no "A" section as per the diagram at front. It is also 0.96mm thick at C, which is the exact difference between the M-AF and M42 registration distances. Seems to work fine at infinity for me and has had zero trouble mounting on the camera (A100).

So not all the adapters out there are poorly designed. Mine doesn't have the ROM in it though, so no focus-confirmation. WHY the camera should require a ROM to talk to to get focus confirm I do not know, particularly when they add the menu option to fire the shutter "without" a lens, so they know people are using non-electronic lenses.
C&C always welcome
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Post Options Post Options   Quote revdocjim Quote  Post ReplyReply Direct Link To This Post Posted: 04 December 2007 at 13:41
I might have gotten mine from the same guy. I think it was like $12 or less. It mounts without any trouble and it is thin so no problems with infinity focus.
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Post Options Post Options   Quote Conny1 Quote  Post ReplyReply Direct Link To This Post Posted: 04 December 2007 at 13:55
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