DxOmark tested the GH2 sensor and the results are somewhat surprising! The Overall score (60 points) is less high than the GH1 sensor (64 points). Click here to see the comparison: GH2 vs GH1 vs 7D at DxO
After the first reviews I thought the GH2 has much better resolution and high-ISO results. What DxOmark states here goes against all other previews we have seen so far!
P.S.: According to DxOmark the Pentax K-5 is better than the Canon 5D. Something must be wrong with their conclusions!
P.S.: Amazon links to the tested cameras specs and price:
Panasonic GH1
Panasonic GH2
Pentax K-5
Canon 5D mark II
Canon 7D
