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02-02-2012, 09:31 AM   #1
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Pentax K5 with 77mm 1.8 Autofocus Lens Align Help

My K5 and 77mm 1.8 combo is missing focus in half of the photos I take. I'm aiming at the eyes and have the camera on center point focus and my sons shirt is in focus. Even in perfect outdoor light in green mode (for test purposes) the camera just misses the perfect shot by producing a soft photo. Can someone please give me a suggestion on how to correct the autofocus issue by aligning my lens. I've noticed the lens sometimes struggles with the autofocus even with plenty of light available. Any suggestions would be helpful. Thank you in advance

02-02-2012, 09:39 AM   #2
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Is it focusing wrong or missing focus? If it is focusing wrong either front focus or back focus that can be corrected. If it is just missing focus, but focuses correctly when it does focus that is a different issue.

I would suggest some controlled tests against a focusing target on a tripod in controlled light. Free focusing targets can be found on the internet with a quick search or you can purchase something like the Lens Align system.

The k-5 does have focusing micro-adjust so if your lens is off a bit it can be adjusted but you should test first to see if that is the issue. It should be consistent, even if wrong so that the micro-adjust can correct. If it is not consistent then I suspect something else is wrong.
02-03-2012, 07:49 AM   #3
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Thanks for the reply. Last night I downloaded a focus chart and spent about an hour aligning my lens. The lens needed a plus 5. When I adjusted it, the camera was way quicker with autofocus and dead on. Before I adjusted the lens it would sometimes hunt in low light and even just before dark with plenty of light. Thank you for the suggestion it made a world of difference and my photos are now sharper.
02-03-2012, 09:29 AM   #4
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Glad that helped!

The k-5 (and many other cameras in that range) provide the micro-adjust because minor differences in manufacturing between camera and lens can cause slight errors in the auto-focus system. These errors are not usually noticeable on 'kit' lenses or other slow lenses but can become noticeable on fast lenses, those with apertures in the f/2.8 or greater range.

It sounds like you have yours dialed in and that's good. However, that should correct miss-focusing not hunting. All the micro-adjust does is move the AF point forwards or backwards. So I would test it again in the same situations where you had problems getting it to lock in before.

I see lots of posts complaining that the k-5 hunts in low light, personally I have never had it hunt in any kind of light so I wonder if I have something setup different that others or just lucked out with a good copy. I often get a hunt and "no focus" error but it is always caused by me trying to shoot closer to the subject than the minimum focus distance of the lens. Moving back a bit has always resulted in a quick lock.

I have it set for center point focus only, and use the AF button on the rear rather than the shutter button to focus.

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