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12-11-2011, 05:19 PM   #16
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Sigh. Right, clearly I'm an idiot to use the 11-point auto-focus setting that the camera provides for me when things are moving quickly and I don't have time to spot focus and recompose, nor select the focus point for each individual shot. Shame on me for not shooting your way/the correct way. And for the record I use 11-point autofocus because the time between finding focus and recomposing can be the difference between getting the expression I wanted and missing it entirely. And I figured the 11 point system is clever enough to guess the focal point when it has a choice between actors, plain grey stage floor or a solid black curtain. It's not the focus system focusing on the wrong thing, it's the focusing system not focusing on anything in the frame. Stop criticising the way I work and be helpful, this is a forum.

Anyway, thanks for the comments. It may or may not have been due to front or back focusing Smeggypants, but I have calibrated the FA 50 1.4 for my K-5, it needed about 8 points of correction, though I've noticed the focus point does change when stopping down, but I was shooting at f/2.0-2.8 so it shouldn't have been an issue. And the focus difference is fairly major, so I'm fairly sure it isn't a fault there...

And the stage focus point isn't underneath any of the 11 points in the system. In the shot where you can see the focus point on the stage, the bit that's in focus is right on the bottom edge of the frame. And as I said, The shots that are out of focus are primarily shots of actors against a solid black background, maybe with some stage floor in if they were further away. The autofocus system literally had nothing but actors falling under any of the points.

I think overall it's just a crappy autofocus system for low light/stage light. I have the latest firmware installed. I suppose if I'm shooting at f/2.8 I can manual focus it. I've done that for a show successfully before on my K-x a while back, but that was at f/4. It does highlight the fact that Pentax's AF system is in dire need of sorting out though, especially considering the price of the K-5.

12-11-2011, 05:32 PM   #17
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QuoteOriginally posted by Mareket Quote
And the stage focus point isn't underneath any of the 11 points in the system.
Define "underneath." The actual size of the AF zones may be considerably larger than you expected; is that a possibility?
12-11-2011, 05:37 PM   #18
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Post a sample image if you can.
12-11-2011, 05:47 PM   #19
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It's literally on the bottom edge of the frame in landscape, unless the AF zones are HUGE I doubt it'd be covered, but who knows? I'll get a sample up tomorrow to show you, and I'll run a few tests to see whether it's down to huge AF zones.

12-11-2011, 07:10 PM   #20
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QuoteOriginally posted by Smeggypants Quote
Actually it does matter. 1.03 did a lot to improve it in low light.
Good to know.

It seemed to really struggle last night when I was taking pictures of the Christmas ornaments on the tree.

I'm at 1.01. Did 1.03 break anything?
12-11-2011, 08:16 PM   #21
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QuoteOriginally posted by Smeggypants Quote
Actually it does matter. 1.03 did a lot to improve it in low light.



Even after AF calibration?
1.03 may have helped in some instances, but it still falls on it's face in the studio. If I use live view AF and f/5.6 or smaller, the AF is just fine.
I don't recalibrate for the studio, I suppose I should, it's easy enough to do, and I generally only use a couple of lenses in the studio.
12-11-2011, 10:28 PM   #22
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QuoteOriginally posted by sebberry Quote
Good to know.

It seemed to really struggle last night when I was taking pictures of the Christmas ornaments on the tree.

I'm at 1.01. Did 1.03 break anything?
No it didn't break anything here.

I would install 1.03 if I were you. anything later only addresses the GPS module
12-12-2011, 04:05 AM - 3 Likes   #23
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QuoteOriginally posted by Mareket Quote
I'll get a sample up tomorrow to show you, and I'll run a few tests
It may also be useful to map out the EV of the scene, according to your camera's metering, to highlight bright or dark areas in the scene, and get an idea of the illumination the AF was working in.

If you open up a JPEG or RAW file in PhotoMe, it can display the camera AE metering in a very informative way as a graphic. It can also display the AF point used in a shot, although not in the same graphic as the AE.

(Shot with the K-x)


12-12-2011, 04:53 AM   #24
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A note about the 1.11 FW: with this it *seems* that my AF lenses are suddenly within -5/+5 of AF fine adjustment in daylight whereas with 1.03 the body replaced for sensor stains needed +10 or more with the DFA 100mm 1:2.8 and the DAL 55-300.

The FW update happened as a part of a warranty repair trip the body took because the DA L 55-300 needed more than +10 in daylight. They *might* actually have added a bit of AF bias trough service menu or something, but from the service comments this was not apparent. They do state, however, that AF was tested and found to perform a-ok and that the problem I'm was complaining about could have been "due to the lens(es)", which I suppose it could (but this raises the question of whether I in fact had an interchangeable lens camera in my K-5 and/or whether my DAL 55-300 was actually an interchangeable lens; I suppose my DFA 100 1:2.8 was barely so needing +10 fine adjustment). Currently the AF fine adjustment settings I have been honing in are: Tamron 17-50 1:2.8: -5, DFA 100: +4, DAL 55-300:+5 (daylight, what happens in tungsten/CFL light remains to be seen as we are into the season where you mostly make do with that or take a break).
12-12-2011, 05:16 AM   #25
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I was trying to adjust my Tamron 17-50 f/2.8 (no serious tripod tests, just handheld focusing at an angle on a page of text). And it seems to me it needs -10 or beyond that (otherwise the focus is in front of the subject). Should I be worrying about this? I did the test in tungsten light (not much light either).
12-12-2011, 05:48 AM   #26
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QuoteOriginally posted by vanyagor Quote
no serious tripod tests, just handheld focusing at an angle on a page of text
I'd start again. That's no way to get reliable results.
12-12-2011, 06:54 AM   #27
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QuoteOriginally posted by vanyagor Quote
I was trying to adjust my Tamron 17-50 f/2.8 (no serious tripod tests, just handheld focusing at an angle on a page of text). And it seems to me it needs -10 or beyond that (otherwise the focus is in front of the subject). Should I be worrying about this? I did the test in tungsten light (not much light either).
I don't want to go off topic and derail this thread, but the Tammy 17-50 has very well known front/back focusing problems. Search it here and on google, lots of posts about it. It's a great lens when in correctable range, mine is fine with -10 on my K20d, and unusable on my K5d..

Pat
12-12-2011, 03:47 PM   #28
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It's your cameras too, not just the lens. See How To Test a Lens Canon Rumors and scroll down to where he tests an 85mm f/1.2 on 5 different copies of 5DMkII.

Also see Variation Facts and Fallacies: Digital Photography Review
12-12-2011, 05:23 PM   #29
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I wouldn't use 11 point AF if I didn't KNOW it was the best thing to use ok? Trust me, it's not a failing in the AF system choosing the wrong point, it's the AF system completely messing up the focus. The autofocus system is smart enough to choose a colourful, contrasty actor or two over a flat, plain grey stage with no contrasty features whatsoever. And the focal point on the stage isn't under any of the zones covered by an AF section. Thanks for the advice, but I'm aware of when I want to use what AF system. Generally I'd manual focus or choose the focus spot, but in fast paced situations I want to be able to compose straight away, not have to recompose after focusing and lose moments. I tried using AF-C in single point AF mode and that was just a complete failure in so many ways. And that was outside, albeit on a cloudy day with the 50-135. It just hunted for focus so often. I'd give it a go if I were you, shooting something moving quickly in low light. It's surprisingly accurate, and it lets you sort out the framing and timing much more fluidly. That's what I find anyway.

Most of the missed focus images are of Actors against a plain background anyway. I only pointed out the stage focus point because I saw form that one image that it had pulled the focus back quite a lot. It was just too dim for the system to work effectively.
12-24-2011, 10:33 PM - 1 Like   #30
Brooke Meyer
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Pentax AF focus in performances.

I've recently finished shooting rehearsals and performances by Jazz & Ballet Companies of their Christmas. Posted a couple thousand photos. Rehearsals when I'm close, I use a DA12-24 and a Tamron 28-75 on my two K-5 bodies. Performances, stuck in back of the house, DA 50-125/2.8 & Sigma 100-300/4. Shot all AF with Single Point and Single Focus using AF button rear to follow. Have callous on thumb. I've never adjusted any lens on any body and if I had couldn''t keep track in the dark.

I threw away a lot of exposures but only a small amount due to missed focus. You can see the results here: Downloads and Prints | Brooke Meyer

The older galleries were done with K-20s. With K-5s, I start shooting at ISO 3200. My most typical exposure ( I shoot manual) is f4 at 1/320, ISO 3200. If needed go to 6400 or 12,800, especially for the Jazz company. I've probably got 45K exposures on 1 body & 20K on the other. One was bought new last Jan at B&H and one was an Amazon open box return. Current firmware. Long range, the 50-135 is wonderful. The Sigma is tougher but when you nail it, its very good. Close up the Tamron 28-75 and DA 12-24 just work very well. I've been doing this for awhile with plays and other types of dance. If there is a design issue with Pentax AF in low light on stage aka Tungsten, I can't find it.
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