[chef]

I bought a used K-x off of fleabay to tide me over while Pentax works out the initial bugs in the K-01. Man I miss the K-7...

This white K-x is in good exterior condition. I immediately noticed that it had severe back-focusing problems. I adjusted to +130 which finally got most photos in focus (18-55mm kit lens and DA 35mm prime). This seems excessive, though other people have posted corrections in the +/- 80 range so maybe that's not unexpected?

It has a tendency to hunt for focus in moderate indoor light. Other cams I've used aren't focus challenged until it gets much darker. Sometimes in bright light or with the built-in flash the photos have a weird ghosting effect (see attached photo). It's a 100% crop of a photo taken with the kit lens @ f/5.6 1/800 ISO-200. Notice how the upward facing edges are smeared, particularly the brightly colored blocks. Indoor shots with the flash have a tendency to smear like this resulting in fuzzy shots. Come to think of it, this happens without the flash too.

I'd estimate maybe 1/3 of my shots are decently sharp. The rest either focus on the wrong location (center spot focus) or end up with the smeared ghosting effect. It's really been frustrating and I'm trying to figure out if I should pursue returning the camera or if this is just the way the K-x behaves.

Thanks for any help!

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[rawr]

All those focus correction numbers (+130, +/- 80) are crazy.

I'd reset all the camera settings, custom settings and whatever DEBUG mode hacks you've made to AF to factory defaults and do no further AF adjustments for a while. You'll probably find your AF works fine.

That image also looks suspiciously like you are using a UV filter on that lens. If yes, ditch the filter.

Also pls just shoot some boring but useful ISO 12233 resolution test charts [PDF 200k) under good stable lighting to check out your lens rather than some random and variable scenes.

And no, this is not how the K-x or the 18-55 DAL normally behaves.

[Christina]

I'm not the most technical, so I can't help you there. But it does look like a camera issue, not a user issue.
The K-x can be a little slow to focus, but once it does, I've found the images to be sharp. I haven't had any sort of "ghosting" problems and have used the K-x for quite a while now.

[twitch]

A 100% crop (edge, centre??) from a wide open shot at the extreme end of a kit zoom range.... well .... don't expect too much in IQ. However the degree of focus adjustment and problems locking focus is more a cause for concern.

[kiwi_jono]

I second reseting all settings. I ended up doing that at one stage.

Agree the AF adjust seems a bit extreme, think mine is around +30 at the moment which is about right for most of the lenses I have.

The photo did not look too bad to me for a 100% crop with 18-55 @55 and wide open at f5.6 (at least from experience with my copy). Especially if this near the image border. My copy is sharper towards the middle of the zoom range (wide open apperture). How does it look at f8 - would expect to see improved.

[chef]

Thanks all for the feedback. The crop is dead center in the original photo. No UV filter.

I did reset all the settings that I could find (one under Custom, another under the Wrench icon group I believe). All custom settings were at default 1 to begin with though. This seems to have marginally helped the auto-focus hunting with the limited testing I've done. The kit lens looks ok with 0 focus compensation after the reset. However switching to the DA 35mm the extreme back-focus compensation of +130 is needed. I've been testing with the focus chart created by a Nikon D70 user.

Often the first time it attempts to auto-focus, I hear the in-focus beep but nothing from the focus motor. Pressing the shutter halfway multiple times will eventually get it to engage the focus motor. If I don't attempt to auto-focus multiple times on a static subject, chances are good (~50%) that the first focus will be off. I've been using a set of standard NiMH Powerex cells that I don't know the condition of. Could weak batteries contribute to the problem? I will test with a set of Eneloop LSD cells when the sun comes back out.

[rawr]

Could weak batteries contribute to the problem?

Yes, very much so.
Stick to eneloops or Energizer Lithiums.

I still can't believe that you require +130 focus compensation, btw. Unlikely unless you have a very badly aligned or damaged lens.

And since the K-x only has one global setting in debug for AF compensation, it must be a hassle to manually enter the AF compensation for every lens you use.

It would probably be easier to deal with your AF accuracy issues by just managing your DOF better, rather than going back and forth with individual AF adjustments for each lens you use on the presumption that a micrometre here or there of AF adjustment will make any real world difference.

[Marc Sabatella]

compensation of +130 is needed. I've been testing with the focus chart created by a Nikon D70 user.

I'd post the test shots. There is a much greater chance the test simply wasn't performed correctly than that the camera needs that much adjustment, although physical misalignment of the focus sensors certainly is possible and does happen.

Often the first time it attempts to auto-focus, I hear the in-focus beep but nothing from the focus motor.

That would be perfectly normal if the camera thinks something within range of the selected focus sensor is already in focus. As would the fact that at some point, it decides to try anyhow, because you have shifted ever so slightly and it now decides to focus on something *else* within range of the selected focus sensor.

[luftfluss]

Can you post an indoor photo with a description of the lighting? My K-x locks focus quickly in a 12' x 18' room illuminated by a 60w bulb, provided the subject has a bit of contrast.

[chef]

I'll post an indoor shot and the ISO chart in the next few days, hopefully by this weekend.

I had used the DA 35mm on a K-7 with good results so I'm hesitant to blame the lens. Maybe the K-7 masked a problem with the DA 35mm? I noticed the K-7 + DA35mm sometimes had very slight back-focus when wide open. Nowhere near what I'm seeing on the K-x though.

Does the eyepiece adjustment (diopter?) have any impact of AF?

Here's what I found researching front/back focusing issues on the K-x :
theunartist set his to +60
https://www.pentaxforums.com/forums/pentax-dslr-discussion/167556-fixing-fron...focus-k-x.html

The writer of this tutorial set his to +70
RiceHigh's Pentax Blog: K-x Debug Mode Tutorial - AF Adjustment