Originally posted by rawr If diopter adjustments didn't do the trick, I'd be reluctant to pursue any shimming until I was completely sure it wasn't a technique issue. OP needs to do more practice with manually focussing in low-light, and shoot a lot more scenes, to make sure it is not just a technique issue related to poor illumination, dim viewfinders and perhaps tired eyes.
If I was a eye doctor, I'd be reluctant to immediately advocate eye surgery if someone came to me and said my vision is sometimes a bit fuzzy. That's what some of these shimming and other suggestions sound like to me.
Of course, but you would advise without any thought that he should first try to cleen his glasses.
And replacing a shim at a K100D is not more difficult as cleaning you're glasses.
TS is lucky that he has BF problems, that means his shim is to thin, so it is extremely easy te fix. T1 is longer than T2, so the focus screen needs to be closer to the lens. (see the picture and the link i posted before)
I should advice TS the same thing as i had done, make a setting with bright daylight, you're cam on a tripod and a focus chart and make some test shots. (for the K7 i did some tests with the viewfinder and some with lifeview.
Also, make some shots with you're right eye and some with you're left eye, just to extra rule out an eye problem.
Make some 10 or so shots with each eye. If all the shots got more or less the same amount of BF or FF, you can be sure it is the shim and not you're eye.
Start with two 1 mm small strips of postit, put you're cam on its back without a lens mounted, and carefully push the release tab of you're focus screen. Flip the focus screen in the direction of the mirror (if it didn't already is in that position), stick the two post-it strips on right and left edge of the focus screen and carefully push the screen and screen plate back to its position and start the test all over.
Repeat this procedure till you you're focus is right on the spot.
Here a link how to replace a focus screen of the K100D, it shows nicely how easy it is to replace the screen or the shim.
http://www.katzeyeoptics.com/files/install6.pdf
Here a link for the best test chart for you're job.
http://www.k10dbook.com/newchart.pdf
There are a lot of charts on the net, but most of them use a small line to focus, but the thickness of the line itself produces focus problems because you don't know on with side of the line you're focus is.
The above chart doesn't has this problem.