remember that the Pentax APS-C format DSLRs only see the central portion of the projected image so you can ignore any of the data beyond 12mm on the horizontal axis. This also applies to comments about vignetting which will be reduced because of the smaller sensor size.

The graphs show MTF in percent for the three line frequences of 10 lp/mm, 20 lp/mm and 40 lp/mm, from the center of the image (shown at left) all the way to the corner (shown at right).
The top two lines represent 10 lp/mm, the middle two lines 20 lp/mm and the bottom two lines 40 lp/mm.
The solid lines represent sagital MTF (lp/mm aligned like the spokes in a wheel). The broken lines represent tangential MTF (lp/mm arranged like the rim of a wheel, at right angles to sagital lines).
On the scale at the bottom 0 represents the center of the image (on axis), 3 represents 3 mm from the center, and 21 represents 21 mm from the center, or the very corner of a 35 mm-film image.