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01-31-2010, 04:21 PM   #16
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it's down to wherever the cutting tool started to cut the thread, radially in relationship to the markings, if they were already on the component, when the parts were machined.

Maybe the lens manufacturers would make an effort to start the thread in the same place in relationship to the lens markings ? More likely the markings were put on after the threading operation and lining them up would entail someone actually 'lining up' the component which would be another operation that probably relied on the 'skill' of the machine operator.

Having worked as a quality manager in a factory where precision turning of mass produced parts were made I somehow doubt that lining up the thread to the markings accurately was considered. Certainly not with old pre CNC technology.
And the adaptor manufactures would be unlikely do it

01-31-2010, 09:15 PM   #17
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OK people, don't kill each other over something like this

If I screw it in without any force, it will be around the 11 o'clock position. Adding some force will get it a bit further (11.30 or so). It's the original Pentax adaptor (as stated in the opening post but maybe I was not clear).

Although I don't know much about the registration distance, logically thinking the 'alignment' influences the distance between the lens and the sensor (similar to a adaptor with a flange) and therefore will not allow focussing at infinity. This was the main reason for asking.

This is theoretially and as this is to a lesser extent than with an adaptor with flange it might not be an issue, I haven't tried it yet as I'm still trying to come to terms with a repaired K10D.
01-31-2010, 11:35 PM   #18
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QuoteOriginally posted by sterretje Quote

Although I don't know much about the registration distance, logically thinking the 'alignment' influences the distance between the lens and the sensor (similar to a adaptor with a flange) and therefore will not allow focussing at infinity. This was the main reason for asking.
"Alignment" truly has nothing to do with the distance between the lens and sensor. Trust me! As long as you are snug against the adapter or body flange you should have no problems. If a particular lens is not able to attain infinity focus when snugged against the flange, the focus ring just needs to be adjusted.

Steve
02-02-2010, 09:42 PM   #19
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Thanks Steve, the dime eventually fell for the snug fit. Took a day or so.

02-03-2010, 10:15 AM   #20
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Makin' lemonade here

QuoteOriginally posted by sterretje Quote
... not exactly at 12 o'clock when I screw the lens in till it can't go further.
I consider this an advantage when using lenses that have aperture rings and wish they were designed that way. The M42 lenses were designed before internal flashes and their @#^%$# extended hoods were added to camera bodies hiding the aperture index from view.

I do what ever I can to intentionally cause the M42 lenses to seat with a 20-30 degree off-set from the 12-o'clock position so I can more easily see the aperture index.

Many adapters can be modified in one way or another to adjust the final index alignment without affecting focus limits.

H2
02-03-2010, 10:55 AM   #21
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QuoteOriginally posted by pacerr Quote
I consider this an advantage when using lenses that have aperture rings and wish they were designed that way. The M42 lenses were designed before internal flashes and their @#^%$# extended hoods were added to camera bodies hiding the aperture index from view.
My previous camera was a Minolta X700 and I could see the aperture index through the viewfinder
02-03-2010, 10:46 PM   #22
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QuoteOriginally posted by sterretje Quote
My previous camera was a Minolta X700 and I could see the aperture index through the viewfinder
Some of the older Pentax 35mm M-class bodies had that feature too. But using non-AE lenses on AE bodies after the 'infernal' flash came along is a PITA.

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02-04-2010, 01:10 AM   #23
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QuoteOriginally posted by Blue Quote
There's no "wrong" place to start. It seems to be more of a relationship to lens brand and adapter.
That's right.

M42 lenses align in varied ways even when using the same adapter, but each lens aligns consistently on an adapter. With my adapter, I get them aligned somewhere between 9 and 12. This is for the best, as it keeps the aperture and distance markings more visible than if they were covered by the flash protrusion.

02-04-2010, 01:44 PM   #24
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The only way I can see that issue possibly being a problem is with a lens like this.

My Super Tak 300mm f4.0

Even then I've never had an issue with the small sensor. I may just try it on film someday soon, and see if it causes any issues on Full Frame.
02-04-2010, 02:04 PM   #25
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QuoteOriginally posted by little laker Quote
The only way I can see that issue possibly being a problem is with a lens like this.

My Super Tak 300mm f4.0

Even then I've never had an issue with the small sensor. I may just try it on film someday soon, and see if it causes any issues on Full Frame.
Now, that is interesting! The mask may well make a difference!

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02-04-2010, 02:16 PM   #26
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QuoteOriginally posted by stevebrot Quote
Now, that is interesting! The mask may well make a difference!

Steve
Even if it does, there's a good chance that I can remove it Steve. Although I never tried.
It looks like only those 3 screws, however I really don't know if it's holding the pin or anything else in place.
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