Panasonic GH1 High ISO RAW
Panasonic GH1 High ISO RAW Image Quality
We've recently started looking at RAW files converted with dcraw, an excellent freeware raw converter. dcraw usually offers timely support for the latest cameras, but more importantly, it does not apply any noise-reduction, sharpening or other corrections such as geometric distortion correction to the output files. (We found that Adobe Camera Raw still applies some limited noise-reduction when its NR settings are set to zero, and it also applies other corrections depending on the make and model of the camera). There will always be differences between RAW converters, in terms of the sort of demosaicing algorithms they use (the processes by which they convert the separate Red, Green, and Blue data sets to an array of full-color RGB pixels), but dcraw seems to use a fairly generic algorithm that delivers good sharpness with relatively few artifacts, and can be counted on to not apply any noise reduction if you don't want it to.
Below are crops from Panasonic GH1 and G1 high ISO RAW files compared to RAW files from the Nikon D5000 and Canon T1i , converted with dcraw. (We compared the GH1 against the D5000 and T1i, as those cameras are close to its price point, and both also offer video capabilities. These are obviously still images, but we felt that the combination of price, video, and target markets made these cameras likely models that might also be considered by potential users of the GH1.)
As you can, the Four Thirds sensors of the Panasonic GH1 and G1 lag behind the APS-C sized sensors of the Nikon D5000 and Canon T1i in terms of noise at all ISOs above about 800. We were surprised by how close the Panasonic GH1 came to the T1i at ISO 800, though. The GH1 seems to have a slight but clear edge over the G1, but its sensor does seem to suffer from more banding. The banding isn't visible in the crops above, but can be seen in the black coffee mug on the right side of the test scene, in all of the dcraw-converted images linked above. Looking at in-camera JPEGs, the banding is only slightly visible in images shot at ISO 1,600 with the normal noise reduction, but becomes more visible as the NR setting is reduced, or under lower light levels. Overall, the Nikon D5000 seems to be the best performer of the group in terms of high ISO noise, but the Panasonic GH1 does quite well for a FourThirds-sensor camera, and has video features (live autofocus during movie recording and full manual exposure control, to name two) that the other cameras lack.