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Old Jun 22, 2007, 6:14 AM   #41
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I would like to thank John, Roy, /\/\ax, Tom, & Dawg for all of the helpfull information on this thread as well as the other one that I started on this subject..

Especially since some misinformation was posted that could have led to my lens falling off the camera!!

The explanations have really clarified for me the reasons & means to modify the M42 to allow the convienence of quick removal like with K-mount lenses..

Now all I have to do is work up the courage to use my Dremel tool on a lens..

Again, many Thanks to everyone!!

Bruce
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Old Jun 23, 2007, 8:44 AM   #42
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John would you be so kind as to post a picture of an M42 lens with a notch in it to allow the lens to lock in place.

Thanks

Fred
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Old Jun 23, 2007, 6:27 PM   #43
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John Hill wrote:
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TDN wrote:
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What he did was grind the adapter until it was thin enough not to make much difference...I guess you could try that with these too...although if it fails, you'll have literally grinded your money away...

Tom
Well not exactly, if you did that you would have something akin to the Pentax adapter with the springy bit removed! You could still permanently mount that on your lens and put a notch in the lens body like I have done.
Which to me is the way to do it if you are nervous about the lens falling off. And yes the adapter will stick on pretty good with out Loc-Tite....but will never come loose with the lock-tite.

Dawg
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Old Jun 23, 2007, 9:41 PM   #44
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Here we go folks, I wonder if this will work!




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Old Jun 23, 2007, 9:53 PM   #45
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Thanks so much for the pictures John!

Fred
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Old Jun 23, 2007, 9:56 PM   #46
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That seemed to post OK!

Now a few comments:

Firstly, this is a small lens and really I did not intend to notch it as the risk of such a lens being inadvertantly twisted off the camera is not great however I was asked to post some pictures so that one got modified this morning.

Secondly, you cannot do this to all lenses. I have a Takumar 300/F4 which did not have sufficient body diameter right in front of the mount thread to put a notch in. For that lens (which is one I did not want to fall off the camera!) I had to turn up a small ring of aluminium which was Loctited in place then notched. I think this process is probably more than many on here would want to get involved in.

Thirdly, my Takumar 200/F3.5 has a tapered body right in front of the mount screw and it would be beyond my metal turning skills to make an aluminium ring for that one. So I cannot notch that lens.

Fourthly, if I was starting from the beginning, knowing what I know now, I would have sought out and bought the flanged (what I call non-flush) adapters which already have a notch to accommodate the locking pin. As far as I can see they are potentially better than the Pentax adapters (can I really say "Better than Pentax" on this forum?) PROVIDED there is no infinity focus issues.










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Old Jun 23, 2007, 10:48 PM   #47
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John ... AFAIK no flanged adapter can provide infinity focus. Mine did not ... so I returned it to fotodiox.com

/\/\ax

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Old Jun 23, 2007, 11:21 PM   #48
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Max, you may be right, I dont know as I have never had my hands on a flanged adapter though experiments I did by unscrewing M42 lens I have indicated to me that the thickness of the flange would not be an issue, at least not with those particular lenses.




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Old Jun 30, 2007, 8:57 PM   #49
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I used a 1/8 inch end mill to do it..Works great. Course having access to a bridgeport mill helps too.

Dawg
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Old Jul 1, 2007, 10:44 AM   #50
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John Hill wrote:
Quote:
Fourthly, if I was starting from the beginning, knowing what I know now, I would have sought out and bought the flanged (what I call non-flush) adapters which already have a notch to accommodate the locking pin. As far as I can see they are potentially better than the Pentax adapters (can I really say "Better than Pentax" on this forum?) PROVIDED there is no infinity focus issues.
Hi John,

Unfortunately, the flanged adapters always have an infinity focus issue as they move the lens farther from the sensor plane by the amount of the thickness of the flange changing the register distance as you have stated.

You might, however, be able to recalibrate the infinity focus of each of the lenses involved by partially disassembling the lens. This probably would also effect the minimum focusing distance. I don't know enough about how this adjustment would be made (and it most likely would be different for each lens), or if the limits of the adjustability for this would make it actually possible for any lens, but if you're only going to be using the lenses on K mount bodies, this would be a reasonable permanent modification (again, if possible).

IIRC, most of the time it involves peeling back the rubber over the focusing ring, loosening the screws that attach the focus ring to the internal helicoil, making the adjustment, then retightening the screws and replacing the rubber. Most of the Taks, again IIRC, don't have rubber covers for the focusing rings, so they would probably involve at least partial dissasembly of the lens. It's always possible that there's a web page showing how this might be done -- there seems to be one for just about everything:-)

I'm sure that a good lens tech could do this (or possibly advise you how to do it) if it's indeed physically possible for the particular lens.

Scott
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