Front back focus calibration on K20D

Hello guys, I recently bought a DA* 16-50 and yesterday I found out that some pictures shot at 50mm f/2.8 were out of focus.

Today I made some test with a couple of objects and it results that my K20D + 16-50 is affected by front focus.

I tried to calibrate it, and here is the result:
(focus on the middle battery, crop 100%)


+0:



+10:





My best result is when the calibration is set to +10. I would like to increase this value in order to improve the autofocus tuning. Is it possible in some way?

Regards,
Andrea

AFAIK +/-10 is as far as it will go. My DA 16-50 is -6 @ 28mm. It may be worth performing a focus test at approximately half way through the zoom range as it may vary at different focal lengths.

Regards,

John

I'm not sure if the global/single (affects all lenses) adjustment and the individual adjustment are cumulative. If they are, you have a max. adjustment range of +/-20

yeah this is tue if you adjust for all lenses with + or -10 then adjust for one
lens,it gives you an extra + or - 10 so you can go to a max of +20 or -20

How recently did you buy the lens? If it won't focus properly even with maximum in-camera adjustment then the lens is defective. Return it to the seller and demand a replacement/refund (or send it in for warranty service if 'recently' means a month or more ago)

Is this a really accurate test? Are you sure those three batteries are exactly parallel to the sensor plane? If that hasn't been measured very carefully and they have all just been placed by eye then the adjustment may not be meaningful.

The idea is that they are NOT exactly parallel to the focussing plane, horizontally anyway. The batteries are at different distances from the lens, the left one being closest.

It's a commonly used 'rough guide', but accurate? It is not.

I wouldn't trust my lenses if the camera was adjusted according to results taken like this.

Yes, I meant in terms of side to side, but perhaps I didn't put that very well...!

But Peter has made the point.

Testing collimation and focusing accuracy is a laboratory standard evaluation IMHO. I'm quite sure if I bought a second hand K10D and was told the focus had been adjusted by the user I would be checking it out very carefully.

Well, actually this is a preliminary raw test, I made this pictures just because some photos of the previous day were out of focus when shot at maximum aperture.

By the way batteries were placed on the corners of square, so the position was a little accurate.

In this week I will try to make further tests with a chart in order to have more accurate results.

I'm not sure the normal global adjustment is really added to the indvidual adjustment, but I've read the global adjustment that can be done via the secret debug menu is.

http://www.google.co.uk/#hl=en&source=hp&q=k20d+debug&aq=f&aqi=g1&aql=&oq=&gs_rfai=&fp=94dc2184ded5623c

I agree with iceblinker. I've not made any test about the individual+global adjustment addition, but the manual clearly specify that the two values are not added.

I know the DEBUG_MODE ON, and I will perform tests with it.

This was my understanding also.

Regards,

John

how far apart are the batteries? ( in terms of distance from camera )