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02-26-2016, 09:32 PM   #1
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Focus Adjustment on K-x - DYI or pay a pro?

For several years I've been using the kit zoom that came with my K-x, with pretty good results (SMC Pentax DA L 18-55mm f/3.5-5.6 AL).

After I started buying some half-way decent primes (see below), I was disappointed to start seeing more of my shots have focus issues. More specifically, my intended subject was sometimes slightly out of focus, but the area just behind my subject was sharp.

I started noticing this with my Pentax DA L 35mm f/2.4. Testing shows my Pentax smc DA L 70mm f/2.4 Limited and my Pentax HD DA 21mm f/3.2 AL Limited are also back focusing an inch or two.

I've read a bit about how the autofocus can be adjusted on a K-x (Debug Menu, MODSET.492 file, etc.), so I know how it's done, in general, but not yet quite enough details to tackle it myself.

Has anyone recently sent a Pentax K-x or similar camera to a service center to have the autofocus calibrated?

If so, where did you send it, and how much did it cost? Do you have to send all your lenses, too?

Thanks

02-26-2016, 11:11 PM   #2
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I did it with my K-x and then with my K-5 myself. It is pretty straightforward.
I followed this tutorial:
RiceHigh's Pentax Blog: K-x Debug Mode Tutorial - AF Adjustment
02-26-2016, 11:37 PM   #3
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QuoteOriginally posted by runswithsizzers Quote
For several years I've been using the kit zoom that came with my K-x, with pretty good results (SMC Pentax DA L 18-55mm f/3.5-5.6 AL).

After I started buying some half-way decent primes (see below), I was disappointed to start seeing more of my shots have focus issues. More specifically, my intended subject was sometimes slightly out of focus, but the area just behind my subject was sharp.

I started noticing this with my Pentax DA L 35mm f/2.4. Testing shows my Pentax smc DA L 70mm f/2.4 Limited and my Pentax HD DA 21mm f/3.2 AL Limited are also back focusing an inch or two.

I've read a bit about how the autofocus can be adjusted on a K-x (Debug Menu, MODSET.492 file, etc.), so I know how it's done, in general, but not yet quite enough details to tackle it myself.

Has anyone recently sent a Pentax K-x or similar camera to a service center to have the autofocus calibrated?

If so, where did you send it, and how much did it cost? Do you have to send all your lenses, too?

Thanks
It is a very easy DYI project. All you need is a tripod and a target. It takes only a few minutes. If you are not happy, it can be reversed with a single button press.

Yvon Borque, a member here, published a detailed description on the web with a pdf of a target. Scissors, tape, and a piece of cardboard is all you need to make. I've used his method with ease and success with four cameras and a dozen lenses.
02-28-2016, 07:00 PM   #4
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OK, thanks for the encouragement.

I just finished autofocus calibration on my Kx, using the debug menu. A plus 130 adjustment made a tremendous improvement in my Pentax SMC DA 50mm F1.8!!

I still need to test my other primes to be sure that adjustment works for them.

Below are before and after shots, 100% crops from the center of test shots made using autofocus with the Pentax SMC DA 50mm F1.8 wide open.

Attached Images
View Picture EXIF
PENTAX K-x  Photo 
View Picture EXIF
PENTAX K-x  Photo 
02-28-2016, 07:50 PM   #5
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Great!!
02-29-2016, 04:46 PM   #6
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Just finished checking the rest of my lenses to see if the +130 autofocus adjustment is going to work. All of my lenses have improved wide-open auto-focus accuracy compared to the pre adjustment photos. More specifically:

HD Pentax DA 21mm F3.2 AL = much improved, tho still a tad soft
smc Pentax DA 35mm F2.4 AL = much improved, but, based on only one test shot, may still have a wee bit of back focus? Softest of the bunch.
smc Pentax DA 50mm F1.8 = as shown above, fantastic improvement!
smc Pentax-DA 18-55mm F3.5-5.6 AL @ 18mm = moderate improvement
smc Pentax-DA 18-55mm F3.5-5.6 AL @ 55mm = moderate improvement
smc Pentax DA 70mm f/2.4 Limited = much improved! probably the sharpest of this lot

All this is based on very limited testing, so I still don't know how much shot-to-shot variation (precision) I can expect using these primes wide open. But I'm delighted to gain significantly better autofocus accuracy at no cost, except for my time. Thanks to Pentax Forums for providing the resources and encouragement to help me get this done!
12-30-2016, 07:03 PM   #7
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I have been trying to fix the auto focus on my dads k-x. I have read in some blogs that getting to the debug mode can be problematic if the camera is running firmware 1.03. Can anybody help me with this?
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