Canon 6D @ ISO 6400 vs Olympus EM5 @ ISO 1600
Link to DPR Test Scene
Photos were converted from RAW with the same settings and then edited.
The editing consisted entirely of the same noise reduction and sharpening applied to both, but the 6D photo had red gamma reduced from 1.00 to 0.92 and overall gamma reduced from 1.00 to 0.94.
Click on photos for fullsize jpgs or here for both fullsize photos on one page.