Dynamic Range: K5 rules!
The Pentax K5 performs well in terms of SNR, but it is even better with respect to dynamic range. The performance is especially impressive at low ISO speeds. Between ISO 100 and ISO 400, the D7000 has exactly the same metrics, but the Pentax K5 takes the lead by providing better DR at ISO 80. And from ISO 800 on, the K5 takes the lead; this tendency is increased from ISO 3200 thanks to the smoothing observed in the K5 processing, although this smoothing alters resolution. So in this case, the advantage also implies an inconvenience.
The A580 does not perform as well as its competitors in the very low ISO settings, being almost 1stop beneath the K5 and D7000. At ISO 400, the A580 metrics match those of the D7000, and remain a little below those of the K5.
If these 3 sensors once again show very close performances, the EOS 60D and the a55 here again show some weaknesses: At low ISO speeds, the 60D is more than 3 stops under a K5 or a D7000. This is huge. The a55 performs a bit better, being “only” 2 stops under a K5 at low ISO settings. But the difference between those two sensors and the top three is more than obvious.