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01-17-2012, 06:06 PM   #1
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Join Date: Apr 2008
Location: UK
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K10D focus problems

My K10D has developed focusing problems. They just seemed to become more and more common, and right now its completely off.

At first I thought it just focused on the wrong place, but then I realized it seems to be horrible front focusing.
These are consecutive images, both focused on the horse, both focused positively a second apart.

The sharpest photo from the day (only about 1.5m)... Testing out the new boots.

This was focused on the lettering is actually isn't too bad, also focused at a distance

No image from this walk is really sharp were it was focused.

I've tried another lens, cleaned the contacts, removed and replaced the focus screen, reset the camera and installed latest firmware.

I've tried to use focus correction in debug mode.
I've managed to get good results for 55mm focusing near and far, as well as with a 70-300mm, by using -450um as correction.

However, with this at 18mm, the lens will only focus very close and does not focus beyond ~3m (it also does not focus well).
In fact, looking at the focus scale of the lens, while at 55mm, the camera can focus on a spot at about 50cm distance and you'll read ~50cm. At 18mm focusing on the same spot at the same distance you'll read ~1m. It focused (beep, hexagon pops up) but its out of focus.
Here are pics from the tests (18mm pics are croped):
-100 um


-200 um


-300 um


-400 um


I don't know what I did to the camera, but if it is a FF issue I created, its unlike what other people experienced because when the compensate its ok for that lens... Mine doesn't even work within the whole range of the lens. Maybe because the compensation required is so large...?

As anyone have any ideas?

01-17-2012, 06:41 PM   #2
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
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Is it possible you hit the mirror. It has a rest on only one side and the mirror alignment has been questioned in the past for suffering long term focus drift.
01-18-2012, 06:34 AM   #3
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Join Date: Apr 2008
Location: UK
Posts: 167
Original Poster
It is possible, but I doubt that is the issue.
No inclination is evident in the mirror and as I understand it a small one would skew the plane of focus from horizontal (as projected onto the screen) into oblique. That isn't perceptible either.

I still would not rule it out. However, in the optical viewfinder both at 55mm and 18mm the image seems to be in focus at the same distance of focus approximately. Meaning, when the object is ~1m away it appears to be in focus when the scale on the lens is at ~1m. With the correction I have dialled in right now, AF seems to work and match the physics from the scales at 55mm, but the AF sets a focus different focus distance for 18mm.
So I don't think there is anything clearly wrong with the physical path through the lens, mirror, focus screen and focus detector.

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