New DA*300 focus lock problem?

Annie X Scuse · 06-30-2014, 12:44 PM

My brand new 300 quite often won’t lock focus even on a sunny, bright day like today. The motor moves OK to what looks like a good focus in the viewfinder but It then clicks a few times, won’t beep to confirm focus, there’s no octagon in the viewfinder and so the shutter won’t release. It therefore leads to missing shots - most frustrating.

Anybody else observed this? Should I be sending this back for replacement?

Adam · 06-30-2014, 12:49 PM

Have you tested for front/back focus? An adjustment may be necessary.

**crewl1** · 06-30-2014, 01:33 PM

Originally posted by Annie X Scuse

My brand new 300 quite often won’t lock focus even on a sunny, bright day like today. The motor moves OK to what looks like a good focus in the viewfinder but It then clicks a few times, won’t beep to confirm focus, there’s no octagon in the viewfinder and so the shutter won’t release. It therefore leads to missing shots - most frustrating.

Anybody else observed this? Should I be sending this back for replacement?

If you can still I would send it back.
If it is so far off front/back as Adam suggests to not lock then I would want to try another unit.

derekkite · 06-30-2014, 11:30 PM

I'll second Larry. It should lock focus in good light without a problem.

What body are you using? Does it focus well with other lenses?

rawr · 07-01-2014, 01:00 AM

What are the switches set to for AF/MF (on camera and lens)?

Annie X Scuse · 07-01-2014, 04:06 AM

Originally posted by derekkite

I'll second Larry. It should lock focus in good light without a problem.

What body are you using? Does it focus well with other lenses?

The body is a K-30. All my other lens (screw drive) focus just fine. Is this hunting an SDM thing?

**crewl1** · 07-01-2014, 06:51 AM

There should not be any hunting just because it is SDM.
And it should be locking on target.
You describe that it does not focus at all which is not normal.
It should be able to focus in the same situations as your screw drive lenses unless your are trying to lock on something that is closer than its minimum focus distance. (140cm)

Annie X Scuse · 07-01-2014, 07:26 AM

Originally posted by crewl1

There should not be any hunting just because it is SDM.
And it should be locking on target.
You describe that it does not focus at all which is not normal.
It should be able to focus in the same situations as your screw drive lenses unless your are trying to lock on something that is closer than its minimum focus distance. (140cm)

It's not that it doesn't focus at all - it does. However, about 30% of the time it doesn't give the focus confirmation 'beep' and so the shutter can't be fired.

**crewl1** · 07-01-2014, 09:37 AM

I'm not familiar with the SDM symptoms as my SDM lenses have been excellent so far but perhaps this is a precursor to the SDM motor going out.
If I had a lens that did not achieve focus 30% of the time in normal situations I would be very annoyed.
If my lenses don't focus it is operator error and I can explain it.
I'm sure you have ruled that out as your other lenses seem to work as expected.

KDAFA · 07-01-2014, 12:48 PM

Originally posted by Annie X Scuse

It's not that it doesn't focus at all - it does. However, about 30% of the time it doesn't give the focus confirmation 'beep' and so the shutter can't be fired.

I experience EXACTLY the same thing in DA*200. I wonder if others do too?

Here's a theory I have for the cause - I can't say conclusively that it's correct, but do think about it, and tell me if it makes any sense, or if it harmonises with your experience.

Are you shooting mainly handheld? I do, and my theory is that the intended point-of-interest may indeed have been correctly (or close to correctly) focused by the camera, but due to vibrations (we're talking handheld here), amplified by the long focal length, the AF sensor is thus seeing not just the intended target but also some other thing(s) close beside it and getting confused, hence the AF algorithm cannot give the confirmation hexagon.

The abovementioned neighbouring object need not even be at a different distance than your intended target point to confuse the AF. It may be about the same distance but perhaps have a different color, texture, contrast or whatever - all leading to the AF confusion that I theorised above.

Just an idea.

fgaudet · 07-01-2014, 01:57 PM

Might sound stupid but is your subject closer than 55 inches? (1.4m)? It took me forever to get accustomed to the DA* 50-135 MFD (minimum focus distance) of about 3 feet. Because the lens will behave exactly as you describe if you're as close or closer than the MFD

06-30-2014, 12:44 PM	#1
Annie X Scuse New Member Join Date: Apr 2013 Posts: 14	*New DA300 focus lock problem?** My brand new 300 quite often won’t lock focus even on a sunny, bright day like today. The motor moves OK to what looks like a good focus in the viewfinder but It then clicks a few times, won’t beep to confirm focus, there’s no octagon in the viewfinder and so the shutter won’t release. It therefore leads to missing shots - most frustrating. Anybody else observed this? Should I be sending this back for replacement?

06-30-2014, 12:49 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	Have you tested for front/back focus? An adjustment may be necessary. 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:

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06-30-2014, 01:33 PM	#3
crewl1 Site Supporter Join Date: Jul 2010 Location: Los Angeles, CA Photos: Gallery \| Albums Posts: 9,807	Originally posted by Annie X Scuse My brand new 300 quite often won’t lock focus even on a sunny, bright day like today. The motor moves OK to what looks like a good focus in the viewfinder but It then clicks a few times, won’t beep to confirm focus, there’s no octagon in the viewfinder and so the shutter won’t release. It therefore leads to missing shots - most frustrating. Anybody else observed this? Should I be sending this back for replacement? If you can still I would send it back. If it is so far off front/back as Adam suggests to not lock then I would want to try another unit.

06-30-2014, 11:30 PM	#4
derekkite Pentaxian Join Date: Sep 2011 Location: Nelson B.C. Posts: 3,782	I'll second Larry. It should lock focus in good light without a problem. What body are you using? Does it focus well with other lenses?

07-01-2014, 01:00 AM	#5
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	What are the switches set to for AF/MF (on camera and lens)?

07-01-2014, 04:06 AM	#6
Annie X Scuse New Member Join Date: Apr 2013 Posts: 14 Original Poster	Originally posted by derekkite I'll second Larry. It should lock focus in good light without a problem. What body are you using? Does it focus well with other lenses? The body is a K-30. All my other lens (screw drive) focus just fine. Is this hunting an SDM thing?

07-01-2014, 06:51 AM	#7
crewl1 Site Supporter Join Date: Jul 2010 Location: Los Angeles, CA Photos: Gallery \| Albums Posts: 9,807	There should not be any hunting just because it is SDM. And it should be locking on target. You describe that it does not focus at all which is not normal. It should be able to focus in the same situations as your screw drive lenses unless your are trying to lock on something that is closer than its minimum focus distance. (140cm)

07-01-2014, 07:26 AM	#8
Annie X Scuse New Member Join Date: Apr 2013 Posts: 14 Original Poster	Originally posted by crewl1 There should not be any hunting just because it is SDM. And it should be locking on target. You describe that it does not focus at all which is not normal. It should be able to focus in the same situations as your screw drive lenses unless your are trying to lock on something that is closer than its minimum focus distance. (140cm) It's not that it doesn't focus at all - it does. However, about 30% of the time it doesn't give the focus confirmation 'beep' and so the shutter can't be fired.

07-01-2014, 09:37 AM	#9
crewl1 Site Supporter Join Date: Jul 2010 Location: Los Angeles, CA Photos: Gallery \| Albums Posts: 9,807	I'm not familiar with the SDM symptoms as my SDM lenses have been excellent so far but perhaps this is a precursor to the SDM motor going out. If I had a lens that did not achieve focus 30% of the time in normal situations I would be very annoyed. If my lenses don't focus it is operator error and I can explain it. I'm sure you have ruled that out as your other lenses seem to work as expected.

07-01-2014, 12:48 PM	#10
KDAFA Veteran Member Join Date: Dec 2012 Posts: 528	Originally posted by Annie X Scuse It's not that it doesn't focus at all - it does. However, about 30% of the time it doesn't give the focus confirmation 'beep' and so the shutter can't be fired. I experience EXACTLY the same thing in DA*200. I wonder if others do too? Here's a theory I have for the cause - I can't say conclusively that it's correct, but do think about it, and tell me if it makes any sense, or if it harmonises with your experience. Are you shooting mainly handheld? I do, and my theory is that the intended point-of-interest may indeed have been correctly (or close to correctly) focused by the camera, but due to vibrations (we're talking handheld here), amplified by the long focal length, the AF sensor is thus seeing not just the intended target but also some other thing(s) close beside it and getting confused, hence the AF algorithm cannot give the confirmation hexagon. The abovementioned neighbouring object need not even be at a different distance than your intended target point to confuse the AF. It may be about the same distance but perhaps have a different color, texture, contrast or whatever - all leading to the AF confusion that I theorised above. Just an idea.

07-01-2014, 01:57 PM	#11
fgaudet Veteran Member Join Date: Oct 2013 Location: Ontario Posts: 726	Might sound stupid but is your subject closer than 55 inches? (1.4m)? It took me forever to get accustomed to the DA* 50-135 MFD (minimum focus distance) of about 3 feet. Because the lens will behave exactly as you describe if you're as close or closer than the MFD