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07-13-2012, 07:16 AM   #1
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K-5 autofocus, thumbs up or down, I am frustrated

I've had the k-5 (and k-20d which I hardly ever shoot) for about 6 months, as well as a bevy of the latest lenses, both Ltd and stm. I came over from Nikon, having shot d200 and d90s. My autofocus miss rate seems to me far far higher w/ the Pentax. If my subject is small-ish, and at mid-far distances I have almost no hope of the camera selecting the right subject. I take a photo of my toddler every week in the same chair, with a 40mm Ltd, from 10-15 feet, in which his feet are obviously closer than his head by a good 2 feet. I shoot w/ a flash in an umbrella, @f/8 usually, and whether I focus (single spot, af-s) and recompose, or select the slight right focus point (which I then turn vertically) it focuses on his feet 75% of the time. I am watching the focus confirmation light... I am getting seriously p*ssed off. I am fresh from an import session, so excuse my vehemence. I have no problem hitting focus when I'm shooting with my 21mm, @f/11, in full sun, with my subject 6 feet away, but it's the more interesting compositions which are blown here. I have read prior threads on the K-5 AF, wherein others seem to struggle too, and I am looking for some succinct responses from people as to whether this AF system is significantly inferior to competitors or not. If you have suggestions I'm all ears, but I'm pretty confident in my process. If there is no way around this issue I will jump ship fast. I won't wait for a $1800 K-3 to get first-rate AF. Once again, sorry for the frustrated tone. Thanks for any insight.

07-13-2012, 07:21 AM   #2
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You should note that the location of AF points in the VF is approximate. My recommendation would be to use the center point to focus, and then recompose for the best accuracy.
07-13-2012, 07:33 AM   #3
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Hi Adam, that's my usual method, but when shooting more critical pics (or especially wide-open) I'd love to take the plain of focus possibility out and just use the focus point that's on my target. I feel like the center point area is large enough that it can still pick a point around my subject, and I can't always tell through the viewfinder that it's chosen "wrong."
07-13-2012, 07:41 AM   #4
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I personally don't recommend the focus and recompose method as it can be problematic. I do, however, recommend getting a new focusing screen. The S-type one from focusingscreen.com is highly regarded on the forum and I can attest to its benefits.

07-13-2012, 07:44 AM   #5
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QuoteOriginally posted by TomTextura Quote
I personally don't recommend the focus and recompose method as it can be problematic. I do, however, recommend getting a new focusing screen. The S-type one from focusingscreen.com is highly regarded on the forum and I can attest to its benefits.
What good is a new screen when using autofocus?
07-13-2012, 07:44 AM   #6
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Hi Tom, is that both for manual focusing and for confirming focus visually in the viewfinder? Is S-type split screen? Thx
07-13-2012, 07:45 AM   #7
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QuoteOriginally posted by weave2d2 Quote
... and I can't always tell through the viewfinder that it's chosen "wrong."
That is certainly an issue with the viewfinder, and it also makes manual focus difficult. That's the main reason I'd prefer a FF (24x36) dSLR - for the larger and clearer finder. If they would just put an MX finder on the K-5...
07-13-2012, 07:45 AM   #8
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From the online DOF calculator, a Pentax K5 with a 40mm lens at f8 at a distance of 10 feet will have a DOF of 6.6 feet. I do not understand how all of your toddler is not in focus.

07-13-2012, 07:51 AM   #9
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QuoteOriginally posted by weave2d2 Quote
I've had the k-5 (and k-20d which I hardly ever shoot) for about 6 months, as well as a bevy of the latest lenses, both Ltd and stm. I came over from Nikon, having shot d200 and d90s. My autofocus miss rate seems to me far far higher w/ the Pentax. If my subject is small-ish, and at mid-far distances I have almost no hope of the camera selecting the right subject. I take a photo of my toddler every week in the same chair, with a 40mm Ltd, from 10-15 feet, in which his feet are obviously closer than his head by a good 2 feet. I shoot w/ a flash in an umbrella, @f/8 usually, and whether I focus (single spot, af-s) and recompose, or select the slight right focus point (which I then turn vertically) it focuses on his feet 75% of the time. I am watching the focus confirmation light... I am getting seriously p*ssed off. I am fresh from an import session, so excuse my vehemence. I have no problem hitting focus when I'm shooting with my 21mm, @f/11, in full sun, with my subject 6 feet away, but it's the more interesting compositions which are blown here. I have read prior threads on the K-5 AF, wherein others seem to struggle too, and I am looking for some succinct responses from people as to whether this AF system is significantly inferior to competitors or not. If you have suggestions I'm all ears, but I'm pretty confident in my process. If there is no way around this issue I will jump ship fast. I won't wait for a $1800 K-3 to get first-rate AF. Once again, sorry for the frustrated tone. Thanks for any insight.
See that thread and the explanations of westmill wich is a Nikon and Pentax user.

https://www.pentaxforums.com/forums/pentax-k-5/177572-all-fuss-about-auto-focus-point-size.html

Keep in mind that AF area sensors are bigger than red squares wich are only indicators of area sensors selected. Focus is made on the more contrasted object in the area sensor selected, may be out of the red square. There is no problem with enough big DOF. With shallow DOF recommandation is to use Liveview with magnification,

AF sensor arrays are indicated by the green and blue lines. Focus is made on the more contrasted object detected by a sensor array. Choose a secure DOF or use Liveview for an ultra precise focus.


Last edited by pscl57; 07-13-2012 at 08:19 AM.
07-13-2012, 07:52 AM   #10
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A few more things...
  • Update your firmware if you haven't already. I just updated from version 1.02 to 1.13 and I think there's an improvement.
  • Also, set up a test with your different lenses and a focusing chart then figure out if you need to use the AF microadjust. It sounds like your DA40 might need it.
  • Avoid using the far right and far left AF points as they are not the more accurate crosspoint type.
07-13-2012, 07:53 AM   #11
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QuoteOriginally posted by Ivor K Ecks Quote
From the online DOF calculator, a Pentax K5 with a 40mm lens at f8 at a distance of 10 feet will have a DOF of 6.6 feet. I do not understand how all of your toddler is not in focus.
Sharpest focus will still be the spot focused on DOF will allow acceptable focus within the range. hat being said there should be about 4 feet behind the main focus point in focus and 2 feet in front.
There is a reason the F8 and be there saying came around, it allowed enough DOF to capture a subject consistently when in a fast paced environement. On APSC in fact it could be f5.^ and be there since the DOF should be about the same as F8 on film

Perhaps a sample showing the issue would be best
07-13-2012, 07:56 AM   #12
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QuoteOriginally posted by weave2d2 Quote
Hi Tom, is that both for manual focusing and for confirming focus visually in the viewfinder? Is S-type split screen? Thx
Yes, it's for both manual focusing and confirming that the AF hit where you wanted it to. It's not split screen. It's a very nice matte that works great with fast lenses, but not so great with slow ones (around f/5.6 and smaller). I wouldn't get a split or microprism screen because it forces you to focus in the center and then recompose.
07-13-2012, 07:56 AM   #13
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I suspect that it is a serious front focusing issue here....
07-13-2012, 07:58 AM   #14
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QuoteOriginally posted by aleonx3 Quote
I suspect that it is a serious front focusing issue here....
it does sound likely

a test with a focus scale (or even a dozen batteries lined up on a 45 degree angle) would quickly confirm the issue
07-13-2012, 08:01 AM   #15
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QuoteOriginally posted by Mike.P Quote
What good is a new screen when using autofocus?
I love having it even though I mostly use AF. It is a big help for letting you know if the AF hit the point you wanted it to.

EDIT: I should add that it's also useful if you use AF to get you most of the way there and then use Quick Shift to tighten up your focus the rest of the way. In my opinion, it's just a better screen all around and it's a joy to use. It's a little pricey being around $100 but the only thing I regret about it is that I didn't get it earlier!

Last edited by TomTextura; 07-13-2012 at 08:10 AM.
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