See this side-by-side test:-
Everything used and the settings are all the same except for a different body. And of course, the test environment and test target are the same, too. It is easily seen that the higher ISO the user selected, the more overexposure resulted with the K-5. Do note also the following additional remarks and comments as provided by the user and the formal response from Metz, regarding the problem, as quoted below:-
"I have tried it on 4 other k-5 bodies and the problem does not exist on my K-r."
"Please be informed, in our company we tested the digital camera "Pentax K-5" (firmware version 1.01 and 1.02) with flash units of our product range and also original Pentax flash units "Pentax AF-540FGZ" and "Pentax AF-360FGZ" and compared the results of images. The results are identical because the camera determines the intensity of flash light."
"However, we found also out by our tests that the precision of Pentax digital camera's "Pentax K-5" P-TTL flash control is not as precise as like with other Pentax digital camera.
It is really bad after all. Why the K-5 should perform worse than the other Pentax DSLRs?! And why the K-r is simply better and provides far more accurate and consistent results?? How come?