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05-14-2014, 01:24 PM   #1
New Member

Join Date: Nov 2011
Posts: 5
Sos 50 1,7

Hello all
There is now month that i am fighting with my pentax A 50 to set focal to infinity
At the begining problem was the A button which was stuck but focus was perfect
I have done my own Solution and now lens only work on A mode but i am happy with that as i always use A mode .
During this operation i have unmount almost every thing including small clunch used for focal and also i have unscrew the two parts of the lens .
After have tried several time my lens has not infinity focus
I have try to screw the two part with diferrent position but nothing .
I have also check several thread but nothing link to my problem so if one pantaxman has any clue it will be very appreciated.

Have good days with good shot

05-15-2014, 07:39 PM   #2
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
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When the two halves are apart, you can freely change the position of the focus ring - the aluminum ring with fine threads that the other half screws into. You can estimate where that ring should be. The ring is roughly in the "infinity focus" position when it's screwed in tight to the lens body, then loosening it about a quarter turn. If you loosen it another half turn, that is roughly the minimum focus distance. I place the ring at that minimum distance. Then loosen it about another quarter turn, Now try to screw in the other part of the lens, just enough to start the focus helix threads. Then use the focus ring to focus the lens. If all the other parts line up in the right place, that is the correct starting point of the focus helix threads. You still have to put the focus grip ring back on and adjust that position correctly, to get the markings correct.
05-15-2014, 09:25 PM   #3
Not a Number's Avatar

Join Date: Mar 2012
Location: Venice, CA
Posts: 4,262
Once you have the helicoid assembled and in the ballpark as outlined above go outside with another lens on the camera and focus on something in the distance and infinity. Replace the lens with your 50mm and with the part of the barrel with the distance scale on it removed, focus at infinity at the same object as with the other lens. Put the indicator ring back on set to infinity and lock the screws down. Check that it still focuses at infinity and the closest focus is 0.45 meters. Normally you would use a collimation rig but this method will work.

This thread may be of use to you on fixing the "A" button problem:
05-26-2014, 04:57 AM   #4
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Join Date: Nov 2011
Posts: 5
Original Poster
Thanks for your answer dave despite your helpfull explanation it still don t map
I have surely missed something .


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