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04-12-2011, 09:58 AM   #16
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there are a lot of different ways, depending on the goal.

I used to think a perminant conversion was the best, as I only had 1 M42 lens at the time. Now, I think a perminant M42 body is better as I have a full set of M42 lenses from 24-200mm.

I also have heard, and this applies to the OP specifically since he is using a long heavy lens, that converting the lens to M42 by only putting a cheap adaptor on without the locking tab, led to a lens falling off because without drilling the lens there is no way to lock it on.

I considered using flanged adaptors and re-adjusting infinity focus, this may be the best way.

04-12-2011, 10:10 AM   #17
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QuoteOriginally posted by Lowell Goudge Quote
...........
I considered using flanged adaptors and re-adjusting infinity focus, this may be the best way.
I believe that is the best way if there is enough adjustment to get infinity focus and one is not too timid to try.

Is there typically enough adjustment available
04-12-2011, 03:47 PM   #18
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QuoteOriginally posted by newarts Quote
I believe that is the best way if there is enough adjustment to get infinity focus and one is not too timid to try.

Is there typically enough adjustment available
On a long lens perhaps as the flange is 0.8 mm and the focus throw of a 400 mm lens could easily be 20 mm. Bit a wide angle lens could be an issue. A 28 mm lens has only about 3-4mm throw
04-14-2011, 01:03 AM   #19
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QuoteOriginally posted by Lowell Goudge Quote
On a long lens perhaps as the flange is 0.8 mm and the focus throw of a 400 mm lens could easily be 20 mm...
An interesting point, this, because it raises the question whether focus throw within the lens (as accomplished by use of the focus ring) is the same as lens-to-sensor throw.

I thought I'd check this out for one of my 135mm lenses, which has its infinity focus shifted to just over 20 feet when I use a flanged adapter. Now, if I use the focus ring to change focus from infinity down to approximately 20 feet, the front element moves out by several millimeters.

This implies that there has to be a significant amount of adjustment in order to counter the effects of a flanged adapter. Does anyone have any practical experience of this? (Because if infinity adjustment is possible and is straightforward to implement, then flanged adapters become very attractive.)

04-14-2011, 06:03 AM   #20
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QuoteOriginally posted by m42man Quote
An interesting point, this, because it raises the question whether focus throw within the lens (as accomplished by use of the focus ring) is the same as lens-to-sensor throw.

I thought I'd check this out for one of my 135mm lenses, which has its infinity focus shifted to just over 20 feet when I use a flanged adapter. Now, if I use the focus ring to change focus from infinity down to approximately 20 feet, the front element moves out by several millimeters.

This implies that there has to be a significant amount of adjustment in order to counter the effects of a flanged adapter. Does anyone have any practical experience of this? (Because if infinity adjustment is possible and is straightforward to implement, then flanged adapters become very attractive.)
I have not got experience with pentax lenses, but with kiron lenses.

I have taken 2 different kiron lenses , one minolta, one nikon mount, and removed the mounts, and used flanged adaptors as mounts, then re-adjusted the focus throw.

In a long lens, the focus throw is substantial, in the order of 10's of mm from infinity to min focus. I cannot see a 0.8 mm impacting the infinity focus to the point that it brings the maximum focus to 20 feet. In ALL old lenses, the entire group moves, and it is the same as an extension . I think there is something else wrong, most likely, the lens was re-adjusted to meet the register distance of another camera, likely a camera with a shorter register distance like a canon.

Last edited by Lowell Goudge; 04-14-2011 at 06:16 AM.
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