以下为600D、GF、GH2、 NEX3 在光圈2.8且1SO 3200下RAW文件帧。

600D lights up/lights down

 GF2 lights up/lights down

GH2 lights up/lights down

NX3 lights up/lights down

(A quick note on the Sony NEX3 lights up shot - my focus was off which accounts for the softness but since we are testing noise it has no effect on the final result). Also since I did not want noise reduction to effect the results I show RAW (not video or JPEG) - this is a pure look at the sensor only.
The test shows some surprises. The NEX3 does well, the 600D not so well but it holds onto colour and contrast a lot better than the GH2, where blacks have turned to a fuzzy purple.
Over well exposed surfaces Canon\'s sensor is the best of the bunch and has a very fine noise grain. But dim the lights and it all falls apart, and a lot of fixed pattern noise becomes apparent.
The GF2 shows what the older generation CMOS sensors look like - awful! But when the lights are on even the GF2 can do respectable ISO 3200.
The GH2 is much improved but it underexposes compared to the others at the same ISO. I believe this is to make the GH2 look better in reviews than it actually is. The GH1 was the opposite way round - considerably brighter than Canon DSLRs at the same ISO setting but of course nosier. ISO 3200 on the GH2 is really more like ISO 2000.
When a CMOS sensor receives a strong signal (plenty of light) it performs well even at high sensitivities. The fixed pattern noise bubbling under is masked by a strong signal. When large quantities of light hits the sensor, noise is cancelled out. That background noise seems to vary quite a bit between CMOS sensors, sometimes even in the same camera. The GH1 for example was notorious for having such a high level of background noise on it\'s sensor that fixed pattern banding was apparent at ISO 100, but the sensors varied so much from camera to camera that some could be considered good performers in low light at ISO 800!
I also believe that some sensors are simply more sensitive than others so they don\'t need the same amount of signal boost.
High ISOs boost the signal, making any noise more apparent. If a sensor is sensitive enough to expose the same shot but with less of a boost, it is going to have less noise because in reality it\'s really operating at a lower ISO than others.

Most reviewers have know for a while now that noise in the shadows is far more noticeable than over well exposed areas of an image, and yet they are still predominantly testing high ISO performance not just in good light but over well exposed test charts with a fast prime.
As these results show DSLR review sites really need to start testing high ISOs in dim lighting conditions at F2.8 instead of with an ultra fast F1.4 prime under studio lighting.

低照度测试应该在暗光小光圈高ISO条件下进行测试的，而不是F1.4演播室灯光。

测试by：EOSHD