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02-09-2011, 11:39 PM   #1
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KX Autofocus

Sorry if this has been already covered.

I should preface my question by saying I know sfa about cameras, so if it's a really stupid question then please pretend it is not and lavish me with false praise.

My KX autofocus is irritating. If I depress the shoot button to get it to AF on something it works initially. When I depress the button further to shoot it proceeds to zoom out completely and then reAF to the exact same point, and then shoot. This process can take 1-2 seconds.

Is this normal? If not, can I fix the problem myself? If not, should I get it repaired under warranty.

02-10-2011, 12:39 AM   #2
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what do you mean by zoom out?

and has it locked before you fully deperss it?
02-10-2011, 01:01 AM   #3
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Are you using live focus?
http://www.photographyblog.com/reviews/pentax_kx_review/
"Live View is fine for use with stationary subjects, but forget it if you want to track a moving subject. The AF system in Live View mode takes several seconds to lock onto the subject, making it much better suited to subjects that don't move."

Last edited by altopiet; 02-10-2011 at 01:14 AM.
02-10-2011, 09:20 AM   #4
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To go over the obvious. Make sure that when you press the shutter button half way that the AF actually locks in before you release it. Second when you go to actually take the shot make sure you did not move and are not focusing at something different. If you fail to do any of these 2 it can cause the camera to need to focus again before taking the shot.

02-10-2011, 11:47 PM   #5
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Thanks guys.

I am not shooting moving subject and am fairly certain that it is locked on (invariably to my child's face) each time.

By zooming out I mean the shot goes completely out of focus (taking quite some time) and then refocuses (quickly) and then I am able to shoot.
02-11-2011, 12:20 AM   #6
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I still don't know if you were using LV or the viewfinder.
Even if you don't shoot moving objects, if you use live view to auto focus, it is very slow. Try switching off LV and use the viewfinder. Also see p143/144 of the manual
02-11-2011, 09:41 AM   #7
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QuoteOriginally posted by dzhay1981 Quote
Thanks guys.

I am not shooting moving subject and am fairly certain that it is locked on (invariably to my child's face) each time.

By zooming out I mean the shot goes completely out of focus (taking quite some time) and then refocuses (quickly) and then I am able to shoot.
usually when I'm preparing to shoot a person, I prefocus and keep my finger on the trigger halfpressed so when something interesting happens, I don't have to refocus (and run into the problem you mention).

Of course, if it's dark, it may be more difficult to get the lens to focus faster. In which case, what I might do if the subject is static is to prefocus and then put the cam in manual focus. This is especially helpful if I want to take a candid shot - when I point the camera a lot of people will tense up, so keeping it low but ready to fire helps me get more real expressions when something interesting happens. The key here is to be able to switch between manual and auto very quickly and to be able to find the switch and know what position it's in without looking. Takes some practice, but it will pay off a lot.

if it's a question of how to get autofocus to work it's best, I've found that using spot select focus (I doubt that's the exact name for it ) and making sure that I'm pointing it at something w/ a fair amount of contrast helps a lot. Also, some lenses focus faster than others - if you're using a slow focusing lens like the kit lens or a macro, it might be best to use some of the prefocusing techniques.

good luck and keep practicing!
02-11-2011, 02:29 PM   #8
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Could it be the K-x is set on AF.A?

AF.A is "automatic" can can select AF.C which does not lock focus -
might try AF.S which does -
anyway from the K-x manual -
which also points out there are some scene modes that does not lock focus (AF.C):




02-11-2011, 05:22 PM   #9
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Thanks a lot ppl, a big help. I will try all of the above
02-16-2011, 09:33 PM   #10
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I have recently downloaded images from the SD card.

A large number are noticeably out of focus (where autofocus had been used to shoot non-moving objects in good light).
02-16-2011, 09:49 PM   #11
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Sounds like you are in AF-C mode, or at the least AF-A. You should be in AF-S to avoid exactly the problem you describe. Hit the info button and you will see the option to change the AF mode.
02-16-2011, 09:54 PM   #12
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Can you post 1 or 2 photo's with the EXIF intact, that might help us, to help you
02-17-2011, 05:48 AM   #13
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You should send it for warranty repair. If you're not in a dark room, it shouldn't do this, not even when the AF.C is enabled. And certainly not outside.
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