Pentax FA-50mm 1.7 Front Focus Issue

**dronegeek** · 01-30-2021, 06:31 PM

I recently acquired a FA-50mm F1.7 and it has a sever front focusing issue. It acts the same on both my K-3 and KP. Even when I set the fine focus adjustment to -10 and shoot the SLRKIT focus adjustment target it looks like +2 is in focus not the 0. The SLRKIT picture shot at F1.7 to narrow the DOF. Does anyone know if there is a way to adjust the lens itself ? See picture. Thanks in advance for any advice.

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Martin Stu · 01-30-2021, 07:36 PM

significant front-back focus most likely cannot be corrected by yourself... unless relatively small...
high-quality repairs can only be done in a specialized workshop or in some specialized service... this may require adjusting the lens together with the camera itself, as I know, a lens without a camera cannot be adjusted separately...

**photogem** · 01-31-2021, 12:54 AM

There are some threads for similar lenses which can be opened at the front for adjustment of infinity:
FA50 disassembly and infinity focus adjustment - PentaxForums.com
SMC Pentax-F 50mm F1.7 Disassembly - PentaxForums.com

**dronegeek** · 01-31-2021, 11:10 PM

Originally posted by photogem

There are some threads for similar lenses which can be opened at the front for adjustment of infinity:
FA50 disassembly and infinity focus adjustment - PentaxForums.com
SMC Pentax-F 50mm F1.7 Disassembly - PentaxForums.com

Thanks !!! that looks helpful !

**TwoUptons** · 02-01-2021, 04:20 PM

Will adjusting infinity focus do anything for focus accuracy?

I’m not sure I understand how that works...

Does the lens focus properly in live view?

-Eric

**clackers** · 02-01-2021, 05:26 PM

Probably a decentred copy, Dronegeek, this is the risk of buying without new warranty. Can you send it back?

stevebrot · 02-01-2021, 05:38 PM

Originally posted by TwoUptons

Will adjusting infinity focus do anything for focus accuracy?

Only if infinity focus is unattainable...

Originally posted by TwoUptons

Does the lens focus properly in live view?

This ^ ^ ^

...or with manual focus using magnified live view. FWIW...slant targets are very problematic.

Steve

**dronegeek** · 02-01-2021, 08:32 PM

Originally posted by clackers

Probably a decentred copy, Dronegeek, this is the risk of buying without new warranty. Can you send it back?

I might have a bad copy which I cannot send back. I have not tried live view with manual focus but it is worth a shot. I can get some sharp shots if I stop down and enlarge the depth of field.

**clackers** · 02-01-2021, 08:45 PM

Originally posted by dronegeek

I might have a bad copy which I cannot send back.

Sad to hear, always a risk buying secondhand without a mechanism (such as PayPal) for refund if defective.

**dronegeek** · 02-01-2021, 08:57 PM

Live view and manual focus performs much better ! See this picture taken wide open. (yes my wife's Christmas Tree is still up....) Thanks for the suggestion!!!

**Just1MoreDave** · 02-01-2021, 10:14 PM - **1 Like**

My guess is that it would help to clean the contacts that report distance to the camera. I don't know if it will work. In the link below, photo 10 shows the contact brush and photo 13 shows the copper strips the brush touches. Some electrical contact cleaner should work. The brush is easy to bend. I would remove the screws, remove the brush, spray contact cleaner on a rag and wipe the brush across the rag parallel with the brushes.

FA50 disassembly and infinity focus adjustment - PentaxForums.com

Like I said, just a guess, but I don't know what else could be adjusted.

ShawnH · 02-01-2021, 11:10 PM - **2 Likes**

I had a lens which fine focus adjustment at +10 was insufficient. My solution was set the camera Fine Focus adjustment to +5 next activate the Debug Mode in my KS2, then use the focus adjustment facility n the Debug Mode to calibrate focus. It worked perfectly. Be advised that all your other lenses will now be shifted -5 points and must be recalibrated. Debug Mode is a bit risky so use at your own risk.

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01-30-2021, 07:36 PM	#2
Martin Stu Pentaxian Join Date: Jan 2019 Posts: 1,115	significant front-back focus most likely cannot be corrected by yourself... unless relatively small... high-quality repairs can only be done in a specialized workshop or in some specialized service... this may require adjusting the lens together with the camera itself, as I know, a lens without a camera cannot be adjusted separately...

01-31-2021, 12:54 AM	#3
photogem Site Supporter Join Date: Apr 2015 Posts: 3,522	There are some threads for similar lenses which can be opened at the front for adjustment of infinity: FA50 disassembly and infinity focus adjustment - PentaxForums.com SMC Pentax-F 50mm F1.7 Disassembly - PentaxForums.com

01-31-2021, 11:10 PM	#4
dronegeek Loyal Site Supporter Join Date: Oct 2016 Location: Euless Texas Photos: Albums Posts: 271 Original Poster	Originally posted by photogem There are some threads for similar lenses which can be opened at the front for adjustment of infinity: FA50 disassembly and infinity focus adjustment - PentaxForums.com SMC Pentax-F 50mm F1.7 Disassembly - PentaxForums.com Thanks !!! that looks helpful !

02-01-2021, 04:20 PM	#5
TwoUptons Loyal Site Supporter Join Date: Nov 2015 Photos: Albums Posts: 4,224	Will adjusting infinity focus do anything for focus accuracy? I’m not sure I understand how that works... Does the lens focus properly in live view? -Eric

02-01-2021, 05:26 PM	#6
clackers Otis Memorial Pentaxian Join Date: Jul 2013 Location: Melbourne Photos: Albums Posts: 16,397	Probably a decentred copy, Dronegeek, this is the risk of buying without new warranty. Can you send it back?

02-01-2021, 05:38 PM	#7
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by TwoUptons Will adjusting infinity focus do anything for focus accuracy? Only if infinity focus is unattainable... Originally posted by TwoUptons Does the lens focus properly in live view? This ^ ^ ^ ...or with manual focus using magnified live view. FWIW...slant targets are very problematic. Steve

02-01-2021, 08:32 PM	#8
dronegeek Loyal Site Supporter Join Date: Oct 2016 Location: Euless Texas Photos: Albums Posts: 271 Original Poster	Originally posted by clackers Probably a decentred copy, Dronegeek, this is the risk of buying without new warranty. Can you send it back? I might have a bad copy which I cannot send back. I have not tried live view with manual focus but it is worth a shot. I can get some sharp shots if I stop down and enlarge the depth of field.

02-01-2021, 08:45 PM	#9
clackers Otis Memorial Pentaxian Join Date: Jul 2013 Location: Melbourne Photos: Albums Posts: 16,397	Originally posted by dronegeek I might have a bad copy which I cannot send back. Sad to hear, always a risk buying secondhand without a mechanism (such as PayPal) for refund if defective.

02-01-2021, 10:14 PM - 1 Like	#11
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	My guess is that it would help to clean the contacts that report distance to the camera. I don't know if it will work. In the link below, photo 10 shows the contact brush and photo 13 shows the copper strips the brush touches. Some electrical contact cleaner should work. The brush is easy to bend. I would remove the screws, remove the brush, spray contact cleaner on a rag and wipe the brush across the rag parallel with the brushes. FA50 disassembly and infinity focus adjustment - PentaxForums.com Like I said, just a guess, but I don't know what else could be adjusted.

02-01-2021, 11:10 PM - 2 Likes	#12
ShawnH Forum Member Join Date: May 2017 Posts: 65	I had a lens which fine focus adjustment at +10 was insufficient. My solution was set the camera Fine Focus adjustment to +5 next activate the Debug Mode in my KS2, then use the focus adjustment facility n the Debug Mode to calibrate focus. It worked perfectly. Be advised that all your other lenses will now be shifted -5 points and must be recalibrated. Debug Mode is a bit risky so use at your own risk.