K10 and DA 16-50 focus issue


douglas1438

Link Posted 23/05/2011 - 09:58
I'm new to the forum and was wondering if anyone has experienced the same problem as me, I'm using a K10 with the smc DA* 16-50mm F2.8.

I get focus lock using the centre point on what I want sharp and then recompose keeping the shutter button pressed half way down. But when I take the photo the image is out of focus. I don't have this problem with my other lenses.

Local camera shop wants to send camera to service centre and have it calibrated to lens.

Any thoughts on this would be much appreciated.

Many thanks,

Chris

karma mechanic

Link Posted 23/05/2011 - 10:08
Leaving aside the added complication of the recomposing, what happens if you get the focus lock hexagon and then simply take the shot - is the intended part of the subject in focus then?
My own website is www.richardgaddphotography.com

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douglas1438

Link Posted 23/05/2011 - 11:00
Not always, although I think it's more by luck. Tends to be worse at f2.8.

Thanks,
Chris

Blythman

Link Posted 23/05/2011 - 11:17
Have you checked that AF is set to AF-S as opposed to AF-C?
Alan


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karma mechanic

Link Posted 23/05/2011 - 11:21
On the K10D it is possible to adjust the autofocus using the normal menus in debug mode, but it is a global setting that applies to all lenses. A lot depends on whether the 16-50 is alone in requiring adjustment or not. Having that lens calibrated by the service centre may be the proper solution, but if it is the body that is out then you've only resolved it for that one lens.

It is worth taking some shots with a tripod of an object that is easy to focus on, ideally on a surface like a carpet or decking so that the plane of actual sharp focus is visible - especially if that plane isn't quite where the object is. Do this with each lens at the widest aperture.

If this shows that the actual focus plane is generally nearer or further than the subject then it may be worth adjusting the body in debug mode. It is easy to do with the correct instructions. If only the 16-50 shows inaccuracy then go for the service centre approach.
My own website is www.richardgaddphotography.com

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i-Berg

Link Posted 23/05/2011 - 11:25
You would expect that focus is more critical with a wide open aperture, so that much is predictable.

Are you able to estimate the distance back or forwards by which the focus is out? Not that the numbers are the issue, just the consistency.

Is it only autofocus that is out (and not manual focus)? Have you tried manually focussing this lens to see what happens?

It is curious that this lens, and no other, behaves in such a way on the same body with the same settings.
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douglas1438

Link Posted 23/05/2011 - 14:23
Thank you for all your advice.

Ok, focus is fine in manual mode, also focus fine on my other lenses, including Tamron 70-200 f2.8 and Sigma 50mm f2.8.

Also tried lens on a K5 body in camera shop and although not a scientific test appeared to be fine. As an aside when I tried to use the lens on my camera after the K7 some features disabled such as exposure compensation, once I'd used one of my other lenses and then gone back to the 16-50 everything was fine again.

Incidentally only purchased the lens in January, thinking back I think a much higher ratio of my shots where out of focus than I'd normally expect.

I'll try your suggested tests.

Smeggypants

Link Posted 23/05/2011 - 19:25
karma mechanic wrote:
On the K10D it is possible to adjust the autofocus using the normal menus in debug mode, but it is a global setting that applies to all lenses. A lot depends on whether the 16-50 is alone in requiring adjustment or not. Having that lens calibrated by the service centre may be the proper solution, but if it is the body that is out then you've only resolved it for that one lens.

I left my K10D permanently in Debug Mode. This way I could dial in the required AF adjustment when I attached a new lens.

Several of my lenses were out of wack AF wise on my K10D. It took less than 10 seconds to dial in the new AF number.

None of my lenses were in focus with the default K10D's 0Ám and most required something between 120Ám and 240Ám
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
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