Pentax A 50 F1.7, focus o infinity

valy · 06-06-2013, 12:24 PM

Tried last night the lens on stars, using live view and 10x loupe find out that the focus is almost there but not quite, it need few mm focus travel to reach pinpoint stars. Anybody have some idea, is a problem of the lens, all are the same?
Thanks.

Adam · 06-06-2013, 12:39 PM

If it goes past infinity, try turning it the other way. Variations in temperature can oftentimes shift the true point of infinity focus.

valy · 06-06-2013, 12:41 PM

No, no past. Tried and there goes to infinity but no reaching the infinity. Hope I made a mistake but... Usually other lenses goes beyond infinity but this stops close to it.

Na Horuk · 06-06-2013, 12:55 PM

I guess the lens was probably disassembled at some point. Does the mount have a normal thickness? There are some lens disassembly guides out there, you can try to get to the focus ring and adjust it. Or send it to some repair store, but it will probably cost around.. 50 euro or so.

elliott · 06-06-2013, 01:20 PM

The Pentax lenses are a little trickier to adjust than many, since the name ring must be removed. It is still a very straight forward process though.

**boriscleto** · 06-06-2013, 02:07 PM

Originally posted by elliott

The Pentax lenses are a little trickier to adjust than many, since the name ring must be removed. It is still a very straight forward process though.

That is true up to the M series. The A series is different.

Here is a good place to start.

https://www.pentaxforums.com/forums/do-yourself/153858-how-remove-fungus-50mm-f1-7-lens.html

https://www.pentaxforums.com/forums/maintenance-repair-articles/179884-pentax...-database.html

elliott · 06-06-2013, 02:18 PM

Originally posted by boriscleto

That is true up to the M series. The A series is different.

Well that is true, the same ring needs to be removed, it just doesn't have any writing on it on the A series.

**Ex Finn.** · 06-06-2013, 03:03 PM

Originally posted by valy

Hope I made a mistake but...

Nope. One of my A-50 1.7`s does the same thing, the other one I have is fine. As far as how to fix it, no idea.

p.s. The problem lens has been owned by me since mid 80`s and never been messed with by anyone.

valy · 06-06-2013, 03:33 PM

Ok, disassemble, but then what to do?

**Ex Finn.** · 06-07-2013, 01:11 PM

Originally posted by valy

Ok, disassemble, but then what to do?

This link might help in figuring out how to tweak the focus, mainly step 3 and 11.
Pentax 50mm repair 1

Na Horuk · 06-07-2013, 03:37 PM

Ok, but if you disassemble it! Make sure you have enough space. Clean space. No dust, no hair, nothing should enter your lens. Have plenty of space and remember what you took apart in what order. And make sure you have the right tools, if you try to force things with bad tools, you might damage things. Good luck

06-06-2013, 12:24 PM	#1
valy Senior Member Join Date: Jun 2011 Location: Bucharest Posts: 120	Pentax A 50 F1.7, focus o infinity Tried last night the lens on stars, using live view and 10x loupe find out that the focus is almost there but not quite, it need few mm focus travel to reach pinpoint stars. Anybody have some idea, is a problem of the lens, all are the same? Thanks.

06-06-2013, 12:39 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,608	If it goes past infinity, try turning it the other way. Variations in temperature can oftentimes shift the true point of infinity focus. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

06-06-2013, 02:07 PM	#6
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,476	Originally posted by elliott The Pentax lenses are a little trickier to adjust than many, since the name ring must be removed. It is still a very straight forward process though. That is true up to the M series. The A series is different. Here is a good place to start. https://www.pentaxforums.com/forums/do-yourself/153858-how-remove-fungus-50mm-f1-7-lens.html https://www.pentaxforums.com/forums/maintenance-repair-articles/179884-pentax...-database.html Last edited by boriscleto; 06-06-2013 at 02:20 PM.

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06-06-2013, 12:41 PM	#3
valy Senior Member Join Date: Jun 2011 Location: Bucharest Posts: 120 Original Poster	No, no past. Tried and there goes to infinity but no reaching the infinity. Hope I made a mistake but... Usually other lenses goes beyond infinity but this stops close to it.

06-06-2013, 12:55 PM	#4
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	I guess the lens was probably disassembled at some point. Does the mount have a normal thickness? There are some lens disassembly guides out there, you can try to get to the focus ring and adjust it. Or send it to some repair store, but it will probably cost around.. 50 euro or so.

06-06-2013, 01:20 PM	#5
elliott Inactive Account Join Date: Dec 2008 Location: North Carolina Photos: Albums Posts: 1,720	The Pentax lenses are a little trickier to adjust than many, since the name ring must be removed. It is still a very straight forward process though.

06-06-2013, 02:18 PM	#7
elliott Inactive Account Join Date: Dec 2008 Location: North Carolina Photos: Albums Posts: 1,720	Originally posted by boriscleto That is true up to the M series. The A series is different. Well that is true, the same ring needs to be removed, it just doesn't have any writing on it on the A series.

06-06-2013, 03:03 PM	#8
Ex Finn. Site Supporter Join Date: Nov 2007 Location: Southern Maryland. Espoo. Kouvola. Photos: Gallery \| Albums Posts: 7,975	Originally posted by valy Hope I made a mistake but... Nope. One of my A-50 1.7`s does the same thing, the other one I have is fine. As far as how to fix it, no idea. p.s. The problem lens has been owned by me since mid 80`s and never been messed with by anyone.

06-06-2013, 03:33 PM	#9
valy Senior Member Join Date: Jun 2011 Location: Bucharest Posts: 120 Original Poster	Ok, disassemble, but then what to do?

06-07-2013, 01:11 PM	#10
Ex Finn. Site Supporter Join Date: Nov 2007 Location: Southern Maryland. Espoo. Kouvola. Photos: Gallery \| Albums Posts: 7,975	Originally posted by valy Ok, disassemble, but then what to do? This link might help in figuring out how to tweak the focus, mainly step 3 and 11. Pentax 50mm repair 1

06-07-2013, 03:37 PM	#11
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	Ok, but if you disassemble it! Make sure you have enough space. Clean space. No dust, no hair, nothing should enter your lens. Have plenty of space and remember what you took apart in what order. And make sure you have the right tools, if you try to force things with bad tools, you might damage things. Good luck