Autofocus issues 50mm with new K5

ptax · 12-04-2011, 11:33 AM

I recently purchased a new K5. I have there different lenses. Two of the three work fine; however, the 50mm SMC FA 1.4 will not autofocus on the K5. It works well on my K10. My other lenses work on the K5.

I can hear the autofocus motor running, but it won't take any pics. Works well on manual focus.

Any ideas as to what could be the problem?

Adam · 12-04-2011, 01:02 PM

What are the other two lenses?

ptax · 12-04-2011, 02:00 PM

The two lenses that work are: Pentax SMC DA 18-55mm kit lens and Tamaron DI 70-300mm

Thanks in advance for any insight you can provide.

Marc Sabatella · 12-04-2011, 03:24 PM

You first said it was an AF problem, but then you said it won't take pictures. That could well be something entirely different. Could you describe in more detail what is actually happening?

ptax · 12-04-2011, 07:35 PM

It will take pics with manual focus, but not when asking it to autofocus. The motor tries to autofocus but never locks in enough to allow for a picture. Sorry for any confusion. I appreciate your trying to help.

twitch · 12-04-2011, 07:38 PM

Have you tried to AF on a high contrast object, something with clear edges of colour/contrast? Or are you shooting a backlit scene maybe?

ptax · 12-04-2011, 07:56 PM

Have tried a variety of lighting situations and photo subjects.

Here is an interesting twist. If I focus on an object using manual focus, get it in focus manually, then switch back to AF, I can take a pic. When on AF it will take a pic if I have it in focus by manually focusing before moving switch to AF. Hmmm. . .

twitch · 12-04-2011, 08:13 PM

You are talking about the FA 50mm 1.4 and not the DA*55mm 1.4??

**crewl1** · 12-04-2011, 08:20 PM

I don't have issues AF with my fa 50. Some things to test:

Does this occur at any aperture setting or only at 1.4? Perhaps it is due to thin depth of field, so try smaller aperture.
Is this occurring indoors in dim light? Try outdoors in daylight?
Clean the contacts on the lens.

ptax · 12-04-2011, 08:32 PM

I will try a greater variety of fixes tomorrow. How would you recommend cleaning the contacts on the lens? It is the FA.

**crewl1** · 12-04-2011, 09:44 PM

I would start by just wiping them off with a lint free cloth. Perhaps add a tiny bit of alcohol to the cloth.
Don't use a method that will contaminate the lens with dust particles, and be sure to blow it off with a rocket blower or similar? before reinstalling on the camera.

RioRico · 12-05-2011, 02:31 AM

I use a teflon pencil eraser to clean contacts, followed by a dust-off. No problem.

ptax · 12-05-2011, 09:15 PM

Woo-hoo!! After lots of agonizing, wondering, posting and cleaning, I noticed a bit of debris located in a little hole just to the right of the lens contacts. Got the debris out and it works like a champ. Thanks to all for the advice to clean. Never would have found the pesky particle without it. Time to take pics!!!

**crewl1** · 12-05-2011, 09:56 PM

Good deal!

12-04-2011, 11:33 AM	#1
ptax Inactive Account Join Date: Dec 2011 Posts: 6	Autofocus issues 50mm with new K5 I recently purchased a new K5. I have there different lenses. Two of the three work fine; however, the 50mm SMC FA 1.4 will not autofocus on the K5. It works well on my K10. My other lenses work on the K5. I can hear the autofocus motor running, but it won't take any pics. Works well on manual focus. Any ideas as to what could be the problem?

12-04-2011, 01:02 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 49,904	What are the other two lenses? 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, 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:

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12-04-2011, 02:00 PM	#3
ptax Inactive Account Join Date: Dec 2011 Posts: 6 Original Poster	The two lenses that work are: Pentax SMC DA 18-55mm kit lens and Tamaron DI 70-300mm Thanks in advance for any insight you can provide.

12-04-2011, 03:24 PM	#4
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,686	You first said it was an AF problem, but then you said it won't take pictures. That could well be something entirely different. Could you describe in more detail what is actually happening?

12-04-2011, 07:35 PM	#5
ptax Inactive Account Join Date: Dec 2011 Posts: 6 Original Poster	It will take pics with manual focus, but not when asking it to autofocus. The motor tries to autofocus but never locks in enough to allow for a picture. Sorry for any confusion. I appreciate your trying to help.

12-04-2011, 07:38 PM	#6
twitch Veteran Member Join Date: Nov 2009 Posts: 4,571	Have you tried to AF on a high contrast object, something with clear edges of colour/contrast? Or are you shooting a backlit scene maybe?

12-04-2011, 07:56 PM	#7
ptax Inactive Account Join Date: Dec 2011 Posts: 6 Original Poster	Have tried a variety of lighting situations and photo subjects. Here is an interesting twist. If I focus on an object using manual focus, get it in focus manually, then switch back to AF, I can take a pic. When on AF it will take a pic if I have it in focus by manually focusing before moving switch to AF. Hmmm. . .

12-04-2011, 08:13 PM	#8
twitch Veteran Member Join Date: Nov 2009 Posts: 4,571	You are talking about the FA 50mm 1.4 and not the DA*55mm 1.4??

12-04-2011, 08:20 PM	#9
crewl1 Site Supporter Join Date: Jul 2010 Location: Los Angeles, CA Photos: Gallery \| Albums Posts: 9,804	I don't have issues AF with my fa 50. Some things to test: Does this occur at any aperture setting or only at 1.4? Perhaps it is due to thin depth of field, so try smaller aperture. Is this occurring indoors in dim light? Try outdoors in daylight? Clean the contacts on the lens.

12-04-2011, 08:32 PM	#10
ptax Inactive Account Join Date: Dec 2011 Posts: 6 Original Poster	I will try a greater variety of fixes tomorrow. How would you recommend cleaning the contacts on the lens? It is the FA.

12-04-2011, 09:44 PM	#11
crewl1 Site Supporter Join Date: Jul 2010 Location: Los Angeles, CA Photos: Gallery \| Albums Posts: 9,804	I would start by just wiping them off with a lint free cloth. Perhaps add a tiny bit of alcohol to the cloth. Don't use a method that will contaminate the lens with dust particles, and be sure to blow it off with a rocket blower or similar? before reinstalling on the camera.

12-05-2011, 02:31 AM	#12
RioRico Veteran Member Join Date: Jun 2008 Location: Limbo, California Posts: 11,264	I use a teflon pencil eraser to clean contacts, followed by a dust-off. No problem.

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12-05-2011, 09:15 PM	#13
ptax Inactive Account Join Date: Dec 2011 Posts: 6 Original Poster	Woo-hoo!! After lots of agonizing, wondering, posting and cleaning, I noticed a bit of debris located in a little hole just to the right of the lens contacts. Got the debris out and it works like a champ. Thanks to all for the advice to clean. Never would have found the pesky particle without it. Time to take pics!!!

12-05-2011, 09:56 PM	#14
crewl1 Site Supporter Join Date: Jul 2010 Location: Los Angeles, CA Photos: Gallery \| Albums Posts: 9,804	Good deal!