I just did a fine-tuning of the AF metering for my lenses paired with the K-7.
The 24mm F2.0 was practically spot on from the beginning (needed only -1 on a scale from -10 to +10), and the 18-55 WR was also quite good (+2), but surprisingly the 50mm F1.4 was way off, needed +7, and so did the 80-200 F4-5.6 (no surprise there though, since the 80-200 is by far the ”worst” lens I have, optically.
The test itself is quite easy to do, I printed out a test chart from http://focustestchart.com/ and placed it on the livingroom table, put the camera on a tripod, aimed the camera at a 45 degree angle down towards the test chart, turned off the anti-shake, put it to the largest aperture possible for the lens and then focused. You have to look really closely at the photos in order to determine where the focus lies (either zoom in as much as possible on the preview in your display, or even better, look at the photos in your computer), but generally you can try adjusting to + or -, take a new photo and see if its an improvement or not. Most cameras that has this feature can remember the different lenses, so you can adjust individually for each lens, even if you have two of the same kind, since it remembers the serial number also.