The Panasonic GH2 features several improvements over the GH1 and the G2, the most important of which is its sensor. On the GH2, Panasonic has chosen an oversized 18.3 million pixel 4/3 sensor, with an actual output of 16 million pixels.
But on the other hand, it might also not be such an improvement for shooting still pictures especially if resolution is not a priority. 18 megapixels on a 17,3 x 13 mm sensor results in a very small pixel pitch: only 3.6 µm on the GH2. This is really small compared to the 4.3 µm of the GH1 or to the 5 µm of a Sony NEX 5, and might impact image quality.
Look at the test results in detail, compared to the GH1, the GH2 shows very similar performance in every field. But most of the time, the GH2 is a tiny bit behind. Its new sensor does not manage to make a clear difference.
Compared to the G2 however, the GH2’s performance has improved: if color depth remains unchanged, the dynamic range gains 1 EV and the low light ISO performance is improved by a bit more than 1/3 stop.
The GH2 is definitely a good upgrade for those who would like better image quality than that provided by the G2. For those already owning a GH1, the choice is between noise and resolution.
Disclaimer: This dxomark review evaluates only the selected camera’s RAW sensor performance metrics (i.e., Color Depth, Dynamic Range, and Low-Light ISO), and should not be construed as a review of the camera’s overall performance, as it does not address such other important criteria as image signal processing, mechanical robustness, ease of use, flexibility, optics, value for money, etc. While RAW sensor performance is critically important, it is not the only factor that should be taken into consideration when choosing a digital camera.