Originally posted by zmohie what camera do you use.
I have many issues with k3. all my lenses has issues with the camera i cant get a proper focus .
my k5iis does well.
Interesting, I have a K-5 and a K-3 and also noticed differences with all lenses. I found out what they have done one the K-3 is to enlarge to AF threshold within which the AF confirm locks. So, with my K-5 + DA*300 , the K-5 refuses to lock if not perfectly in focus, and the K-3 is accepts to lock with the same unperfect focus as observed with the K5. The K-3 AF lock is more tolerant from lens to lens (relative to K-5) but slightly less accurate.
Regarding the problem with the DA limited, if I photograph a tree at 7 meters, the K-3 AF locks but the tree is blurred and the far ground (building at 100meters) is tack sharp. I can only have the tree sharp by refocusing by hand.
With cheap Tamron 17-50, or Tamron 18-250, or DA 18-55, the tree is tack sharp, as it should be.
---------- Post added 02-26-15 at 05:04 PM ----------
Originally posted by Na Horuk Yes, all DA limiteds have a completely broken autofocus lol just kidding, of course not!
There are many thread about AF, but to be honest, often we find out the actual fault is with the users, once they post some sample photos. Blur can be caused by handhsake, pressing the shutter button, even slightly long exposure (slow shutter), shallow DoF, mirror slap, SR, moving subjects, and so on. It also often happens that the AF works, but it locks on an object the user didn't want, for example if the background is contrasty, or if auto AF point selection is enabled. PD AF and CD AF are completely different from each other, and it is unlikely that CD AF would have a consistent front or back focusing. But CD AF has a bigger chance on locking focus on something that is technically the most contrasty object, but is not what the user wanted. With PD AF, the AF points are much bigger than those little overlays you see in the VF. The centre AF point is (depending on camera) about as big as the ( ) in the middle. So it is very possible that focus is locked on one part of the AF point, but not the part the user wanted.
It is possible you got a bad lens, but it is not a likely thing to happen. Some play with the AF ring is no problem, as it doesn't necessarily move the focus, its just the space between gears. And that wouldn't affect AF performance much, anyway.
But like I said, there are many threads about AF. About AF calibration, using focus charts and many different techniques. Feel free to look them up. There is an in-camera setting to help with AF adjustment. Thing is, there are certain tolerances in the factory, and if the specific lens and specific camera you have are on opposite sides of the tolerances, this might lead to a consistent small error. So it is possible that camera and lens are within spec, but need to be tuned together. AF calibration can fix this. And its also possible the problem aren't lenses, but the camera. Maybe you already have a faulty AF correction setting.
If you want perfect calibration out of the factory, go buy Leica gear. That is the difference in cost.
I can't give any more info than that without seeing sample photos with exif data.
I use different lenses, 18-55 @ 40mm f5.6, 17-50 @ 40mm f5.6, 18-250 @ 40 f5.6, DA 40 Limited @ f5.6, exactly the sames camera settings for all lenses and a tripod. The variable parameter is only the lens. All lenses works fine with K-5 and K-3; except the DA 40 that give a blurred target (tree) placed a around 7 meters, and tack sharp background. Same problem with CDAF and PDAF , fine AF adjust has no effect (so I assume it is not a problem of front focusing/back focusing).
On this Pentaxforum web site, I found the comparison between the DA 35 2.4 , DA 40 Limited (
https://www.pentaxforums.com/reviews/da-35mm-40mm-limited-xs-shootout/image-q...sharpness.html) and I get similar unsharp photos as Pentax forum, but the repair center said that my lens is fine !!! So , either the repair center did not bother spending time on this lens because they had more valuable things to do (in this case they are fooling me...) or I don't understand. Should I complain to Ricoh that their third party repair center is unprofessional ?