K3 focus issues most confusing

I am having a very low success rate in getting K3 + DA*300 images in focus compared to my K30. Probably only 40% in focus. But worse still I can't see why. Take this butterfly shot. It is at 1/4000th sec. I know the DOF is very shallow but it confirmed focus on centre spot on the butterfly's head. I'm getting the same with birds in that when the centre spot lacks contrast it confirms it but then focuses on something nearby instead.
This image is even more confusing in that at first it looks like it has front focused but the rear antenna and edge of back petal of flower are sharper than the front antenna! The combination is stunning when it gets it right but it is getting very frustrating on the number of missed shots the camera is confirming as in focus. Any ideas?



Cropped

What is your aperture set at?

In this shot it is F4. By the way, before anyone says - I wouldn't normally be taking butterflies that wide open! It doesn't alter the fact that the wings are blurred but the petals behind and grass in front are sharper.

Have you calibrated to AF of the DA*300 to the K-3, using the AF Fine Adjustment Dave? If not, this would be the first thing I would do.

I have to calibrate all my lenses with each camera, the longer the lens the more critical this becomes.

As an aside, I've found the focussing on my K-3 to be very accurate and consistent, with all lenses tried so far. The Sigma 150-500 seems very good with this combination, as for the DA*300, well I don't have one yet, but hope to get one pretty soon, so I will report back then.

Regards
David

Doesn't help I know, but this has been reported elsewhere, affecting a low number of bodies. link

Only remedy seems to be change the body, although one tog reported 'success' with a global +10 setting in AF Adjustment; odd though, as I would have thought all his shots would be oof?

Additionally Dave, I would get your K-3 checked if I were you. It could have some mis-alignment of the mount or sensor - this would possibly create the effect you are seeing. If the alignment of the sensor is not parallel, the there will be a difference in the focal plane across the frame of the image - this looks suspiciously like what you may have. I haven't noticed anything like this with my K-3.

However, you've got me thinking now and I had very similar issues with my first K-5. The damn thing was so inconsistent with focus, particularly with the DA 17-70, sometimes it back-focussed, sometimes it front focussed and occasionally it got it right! I haven't had any other bodies that exhibited this behaviour and it was only with certain lenses, also the same lens on other bodies behaves perfectly!

Regards
David

It is evident that subject matter behind and in front of the butterfly are in focus. I'm sure you've done this, but if not, check your lens for grease marks or blemishes on the sensor. At these shutter speeds, I would be surprised if the problem is subject movement.

Another thought Dave, try taking some images of a page of small text at an angle, this would clearly show if there are areas of the images not consistently in focus across the frame and any differences in front/back focus. Ronnimac's suggestion above is a good one - if there is any smearing of anything on the sensor, no matter how small and slight, it may create issues.

Regards
David

Thanks for all of the suggestions. I have calibrated my lenses but I think the DA*300 has reverted back to 0, perhaps when I upgraded the firmware. I'm not sure many of the above could cause front and back focusing at the same time, plus perfect images sometimes, but I will try them !
Dave

Checked - definitely nothing on the lens or sensors. Read that link on the other forum and it does sound a bit like my problem. I just keep looking at that pic and thinking - How can the front stuff be in focus but the back antenna be sharper than the front but the wings be so soft? What if the lens was right at its minimum focus distance. Could it be focusing on the back antenna which is far enough away to just be on the minimum and the leaves at the front because they are actually off at angle so further and back within the minimal focus distance? I was pretty close to the subject on thinking about it.

That's not a bad supposition Dave. The page of text suggestion I made would rule out any unusual variances across the frame and may confirm if you are correct here.

Regards
David

I think that was it! Panic over. CAn't think of a better explanation. This one taken in same spot today with perhaps more thought and time:-

That's much better Dave! BTW, got my DA*300 last night, it was dark when I got home from work so tried a few shots today. First impressions are that focus is absolutely nailed on with the K-3, no adjustment required and boy is this lens sharp wide open! Can't wait to get some birds and butterflies in range!

Regards
David

Looking forwards to seeing them David. That's the crux - F4 is sharp, makes a lot of difference in wildlife.