Updated (2-10): My Observations on the Results Added!
Well, people continue to complain about the vigorous mirror slap and the low SR performance of the K-x. Here are yet two recent examples:-
I think it is of no harm to check my current K-x against one of my Canon L lenses for a SR Vs IS Shootout and comparison. I would pick my 24-105 L and mounted it on my 5D to test it against the K-x with the DAL 18-55 kit lens mounted .
Now, the test procedures and conditions are as below, followed by the results as tabulated:-
1. The 24-105 L is zoomed at 70mm, in-lens IS turned on, 3 shots were taken handheld for each of the Shutter Speeds in Tv Mode at 1/30, 1/15, 1/8 and 1/4th of a second, that is, -1.222, -2.222, -3.222 and -4.222 Stops (S)lower than the Theoretical Safety Shutter Speed Limit of 1/70s, Respectively;
2. The 18-55 DAL is zoomed at 45mm (Effective AOV near 70mm 135 FF equivalent), in-body SR turned on, 3 shots were taken handheld for each of the Shutter Speeds in Tv Mode at 1/30, 1/15, 1/8 and 1/4th of a second, that is, -1.222, -2.222, -3.222 and -4.222 Stops (S)lower than the Theoretical Safety Shutter Speed Limit of 1/70s, Respectively;
3. Other Settings: Tungsten Preset WB (Light Source: Pure Tungsten, Philips Bulbs), ISO 800, Single AF Mode with Central Point, All EXIF Preserved;
4. I tried my best to stand straight, hold my breath, hold the cameras and took the shots. The pictures are obtained as below, which are all resized to 2592 pixels in width at the Same Size. It is therefore there are 3 x 4 pictures for each of the cameras. So we have 12 x 2 pictures in total for two cameras. You can click on any of the thumbnails to view the Large Picture, a new Window/Tab will be opened. Endless Measurbation begins! :-D
Well, your Conclusion(s)? :->
P.S. My current K-x unit is already the best in terms of mirror slap vibration amongst the 3 K-x units that I have touched, used and tested so far. This is of nothing scientific, though, but just personal observation and impression of mine. You can take my this remark as a grain of salts anyway. But on the other hand, the above test should have shaded some light on how the Pentax SR system is performed and compared.