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03-03-2015, 08:06 AM   #16
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QuoteOriginally posted by edri Quote
Original adapters allow always correct alignment
Not on my systems; they're always off a bit (10-20 degrees or so). But it's a non-issue for me.

03-03-2015, 09:26 AM   #17
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QuoteOriginally posted by jatrax Quote
Exactly. Many ways to make this work. I paid $30 for a real adapter. And $20 for 5 knock off adapters that I threw in the trash. I'm glad you got good ones, but it really is a gamble whether you get good ones or junk. The real ones always work, the knock offs might work. And only if you remove the spring that keeps the lens from falling off accidentally.

If you are happy with your method, great.
What he said. My personal experience with brand-x adapters was sufficiently poor that I refuse to mount them to any of my cameras. This opinion extends to even the common practice of removing the retention spring.*

I know many users on this site have had good experience with the cheapo versions, but I cannot recommend them as a budget solution, particularly to anyone inexperienced in using adapted lenses.

Steve

* How does metal shards found in mirror box sound? Over-rotation in the mount, anyone (important if used on film cameras)? Overly tight mount? (The adapter is supposed to fit loosely in the mount opening and should snug up the lens flange against the face of the k-mount as the lens is mounted. This is important to insure infinity focus.)
03-03-2015, 09:35 AM   #18
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QuoteOriginally posted by edri Quote
The main problem, indeed, is the alignment index (aperture, focus) on the lens. For cheap adapters, each has a different alignment, they are not two similar. For one the the lens inscriptions are offset by about 180 degrees!
QuoteOriginally posted by edri Quote
Original adapters allow always correct alignment
This last assertion is most definitely not true.

As for the general expectation of index alignment, 180 degrees is indeed excessive, but be aware that the alignment of the index mark to the camera is highly variable, even with the M42 bodies mounted with M42 lenses. I own five M42 bodies (3 Pentax, 1 Mamiya/Sekor, and 1 Ricoh) and no combination of lens/body result in a mount with the index to the 12:00 position. This is true regardless of the lens maker. None of my Takumars mount at 12:00 with any of my Pentax bodies. Likewise, I have two genuine Pentax M42 adapters. The position of the thread entry is different on both. This is true for the lenses too. I have over a dozen M42 lenses and only one combination of adapter/lens results in the index mark being at 12:00.* That is with an early 70s Vivitar 135mm lens with one of my two genuine Pentax adapters.


Steve

* The reason for this is fairly obvious to anyone having experience using taps/dies for cutting threads. I suspect that it has traditionally been deemed unnecessary to put much effort into making sure that the entry points for the thread ramp be consistently at a particular point. The aperture actuator coupling in the camera is good evidence of such. On the Spotmatic, it describes about 45 degrees of arc!

Last edited by stevebrot; 03-03-2015 at 09:50 AM.
03-03-2015, 11:22 AM   #19
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I compared with the deviations caused by cheap adapters with Pentax DSLRs. Compared with a deviation index of 30-180 degrees, original adapter provides a correct alignment. A few degrees does not matter, you can read indicators on the lens.

03-03-2015, 01:13 PM   #20
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I have 2 genuine adapters marked "Pentax Philippines" and one marked "Pentax Japan". My M42 lenses all line up around the 11 o'clock position which is about 30 off from 12 o'clock on all three of these.

I have a M39 (Leica) to M42 adapter ring from Fotodiox. It will not thread into either of the Philippines made adapters but threads smoothly into the Japan made one.
03-04-2015, 08:58 AM   #21
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QuoteOriginally posted by Not a Number Quote
My M42 lenses all line up around the 11 o'clock position
That is pretty typical, even for M42 bodies. I have heard various theories as to why 11:00 position over 12:00, but I think they are all guesses. After all, the aperture actuator is 180 from the focus index and at 11:00, it is perilously close to not engaging the actuator in the body!*


Steve

* I know, I know...only applies to M42 bodies...
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