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12-11-2011, 09:00 AM   #1
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K-5 Missing focus by a mile

I shot another performance recently with the K-5 and the FA 50mm f/1.4, and whilst I got some excellent shots, I had a lot of trouble dealing with the camera totally missing the focus for quite a few separate moments during the performance. It generally focused about a metre and a half or so in front of the target for seemingly no reason. It was on 11 point auto, and I was trying to point it towards high contrast areas to help it in low light, but even in decent lighting it was missing some shots. You can see the focus point on the stage floor in front of the actors, but there is no reason it would lock focus on that point, as the floor is just solid black/dark grey. What could have caused this? And it's focused wrongly far too much for it to be a back focusing issue.

Twas really irritating, and got in the way of a lot of important shots. The K-5 autofocus sucks in my experience I genuinely have better luck manual focusing a lot of the time in theatres, even in full lighting.

Also, a question for Canon/Nikon users, does AF-C (or the equivalent in your camera) constantly follow the subject, or does it adjust every half a second or so to catch focus again like the K-5 seems to do? Or is that just the K-5 being the K-5?

12-11-2011, 09:14 AM   #2
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I recently bought a Samsung NX10 and while its high ISO sucks, I'm often amazed by how accurate the contrast focusing is. I haven't always been so impressed with my Pentax DSLRs (K20D, K-x, K-5) which tend to focus a bit more randomly with the phase AF. One of the Achilles' heels of Pentax.
12-11-2011, 09:17 AM - 1 Like   #3
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If you opt to use 11 point auto, the camera's AF algorithm may not be intelligent enough to pick the right spot in high contrast situations. Simply put your camera cannot second guess where you want it to focus when you set it to full auto, particularly in difficult lighting situations. Why blame the camera when you should have taken full control and selected the AF point manually.
12-11-2011, 10:39 AM   #4
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I don't like if the camera decides on the focus point. I had a P&S that did that after waking up from sleep mode and it was the reason for me to buy my first dSLR.

Don't have experience with other makes, so can't answer the second part of the question.

12-11-2011, 11:28 AM   #5
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What firmware is the OP running? Not that it really matters, Pentax dropped the ball with the K5 WRT AF. I have the same problem in the studio shooting under modeling lights. The AF isn't accurate enough and it front focuses.
12-11-2011, 12:19 PM   #6
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QuoteOriginally posted by Wheatfield Quote
What firmware is the OP running? Not that it really matters, Pentax dropped the ball with the K5 WRT AF. I have the same problem in the studio shooting under modeling lights. The AF isn't accurate enough and it front focuses.
When K5 first arrived, everybody was raving about the accuracy of AF. What happen since?
12-11-2011, 12:30 PM   #7
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QuoteOriginally posted by song_hm Quote
What happen since?
Must have had a bad batch of mind-reading modules, wonder what serial numbers are effected.
The good news is that the center point focus still seems to function to some degree.

Sorry, could not help it.

Last edited by Ex Finn.; 12-11-2011 at 12:47 PM.
12-11-2011, 12:37 PM   #8
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QuoteOriginally posted by Mareket Quote
It was on 11 point auto
I fail to see the advantage of letting the camera decide where to focus, unless I was bored and just wanted to mess around.

12-11-2011, 12:41 PM   #9
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QuoteOriginally posted by song_hm Quote
When K5 first arrived, everybody was raving about the accuracy of AF. What happen since?
They did?
I remember a lot of problems with low light AF and a lot of forum discussions about it. Although some people never admitted there was a problem (it was all imaginary or user faults) Pentax released a new firmware that improved the situation somewhat, but didn't cure it entirely. At least not for my K5.

Then the summer came and for me (in Sweden) the low light problem disappeared with the sun. Now the winter is here and the sun is gone (well almost) so the problem is probably back to, don't really know as I sort of avoid it now...
12-11-2011, 01:44 PM   #10
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QuoteOriginally posted by Mareket Quote
It was on 11 point auto,
If you knew what you wanted the camera to focus on, centre-spot AF would probably have been more appropriate for that type of scene. Using 11 point auto AF to shoot a stage scene full of brightly lit, contrasty elements was asking for trouble. In the absence of face-detection, how was the camera to know you wanted it to focus on the person?
12-11-2011, 03:57 PM   #11
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QuoteOriginally posted by song_hm Quote
When K5 first arrived, everybody was raving about the accuracy of AF. What happen since?
Tha AF accuracy is craptastic on low tungsten light levels, which as it happens, is what studio modeling lights are.
It's fine in pretty much any natural light.
12-11-2011, 03:59 PM   #12
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QuoteOriginally posted by Wheatfield Quote
What firmware is the OP running? Not that it really matters, Pentax dropped the ball with the K5 WRT AF

Actually it does matter. 1.03 did a lot to improve it in low light.

QuoteQuote:
. I have the same problem in the studio shooting under modeling lights. The AF isn't accurate enough and it front focuses.
Even after AF calibration?
12-11-2011, 04:02 PM   #13
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QuoteOriginally posted by Mareket Quote
I shot another performance recently with the K-5 and the FA 50mm f/1.4, and whilst I got some excellent shots, I had a lot of trouble dealing with the camera totally missing the focus for quite a few separate moments during the performance. It generally focused about a metre and a half or so in front of the target for seemingly no reason. It was on 11 point auto, and I was trying to point it towards high contrast areas to help it in low light, but even in decent lighting it was missing some shots. You can see the focus point on the stage floor in front of the actors, but there is no reason it would lock focus on that point, as the floor is just solid black/dark grey. What could have caused this? And it's focused wrongly far too much for it to be a back focusing issue.

Twas really irritating, and got in the way of a lot of important shots. The K-5 autofocus sucks in my experience I genuinely have better luck manual focusing a lot of the time in theatres, even in full lighting.

Also, a question for Canon/Nikon users, does AF-C (or the equivalent in your camera) constantly follow the subject, or does it adjust every half a second or so to catch focus again like the K-5 seems to do? Or is that just the K-5 being the K-5?
Is it? Have you calibrated the AF for your FA 50/1.4 ?

I have the same lens model and it severely back focusses on both my K5s. I have had to dial in -10 and -7 respectively to compensate.
12-11-2011, 04:05 PM   #14
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QuoteOriginally posted by Gimbal Quote
They did?
I remember a lot of problems with low light AF and a lot of forum discussions about it. Although some people never admitted there was a problem (it was all imaginary or user faults) Pentax released a new firmware that improved the situation somewhat, but didn't cure it entirely. At least not for my K5.

Then the summer came and for me (in Sweden) the low light problem disappeared with the sun. Now the winter is here and the sun is gone (well almost) so the problem is probably back to, don't really know as I sort of avoid it now...
I bought a K5 post sensor stains but early this year. it had severe low light AF problems. 1.03 didn't cure it at all. I had it replaced and then bought a 2nd K5. The two newer K5s came with 1.01 and exhibit low light AF problems. this time 1.03 did help a lot, but didn't cure the problem completely.

I hope Pentax sort the AF properly for the K3
12-11-2011, 04:57 PM   #15
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QuoteOriginally posted by Mareket Quote
You can see the focus point on the stage floor in front of the actors, but there is no reason it would lock focus on that point, as the floor is just solid black/dark grey. What could have caused this? And it's focused wrongly far too much for it to be a back focusing issue.
The AF will try to pick the object closest to you, and if you're in 11 point AF, the camera might pick the stage to focus on, since it may have been the closest thing to the camera in view when you took the picture.

Like others said, you should pick center point AF or select the AF point yourself. Or make sure you don't include objects closer to you than you're subject if you want to track the actors with 5 or 11-point AF.
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