Tuesday, November 6, 2007

Comparison of G3 and G9 ISO 400 RAW

One of my reasons for getting the Canon G9 when I already had a G3 was to get a higher useable ISO rating. The G3 has a maximum ISO 400 whereas the G9 goes up to ISO1600. Much has been made of the fact that the G9, having 12 megapixels, necessarily has smaller pixels than the G3 with its 4 megapixels. Small pixels generally mean more noise. Even so, it seemed likely that the G9 might be more useable at, say, ISO 400, than the G3. I decided that if the G9 produced reasonably good 8x10 prints at ISO 400 – even if special noise reduction was required -- then it would be a keeper. This turns out to be true and I’m keeping the G9.

The picture below is a direct comparison of the G3 and G9 at ISO 400. Once again, it is important to know the “rules” of the comparison. The scene is the same as in the previous post. The G3 and G9 were set at ISO 400, RAW mode and aperture priority (Av). The cameras were placed, one at a time, on a tripod; the tripod was not moved. RAW files were processed in Adobe Camera Raw (ACR) with no adjustments; that is, all tonal adjustments, sharpening, noise reduction, etc were set to zero. (Keep this in mind when looking at the crops.) Even so, there are some important differences in the basic image files. The G3 image is naturally 2272x1704 pixels; the G9 is 4000x3000. The G3 lens was at its widest, 7.2mm focal length but the G9 widest focal length is 7.4mm. Even though the tripod did not move, the cameras were not precisely oriented. The G3 exposure was 1/1250 sec at f4.5 but the G9 selected 1/640 only about five minutes later. Rather than manually adjust these automatic exposures, I decided to accept them; the histograms look about the same.

Again referring to the previous post for the complete view, the sample below is from the bottom towards the middle.

On a 100% pixel view, the G9 image is larger. How should this be resolved? I decided to reduce the G9 image to the exact same number of pixels as the G3 (G3 and G9 images have the same aspect ratio). The above is a 100% crop showing 400x400 pixels (click on the picture for a larger view) of the (essentially) unprocessed RAW images. Clearly the G9 crop has less noise and shows more detail.

The above area was well exposed; let’s examine another sample from the shadows. The crop below compares the G3 and G9 at the middle right hand side of the full image. The rules of comparison are the same.

Once again, it is easy to prefer the G9 image. Perhaps the most obvious improvement of the G9 as compared to the G3 image lies in the amount of visible detail. Notice that the G3 sky shows more noise. Interestingly, the amount of noise in the shadows seems roughly equal but, again, the G9 image has much better detail and gives the impression of less noise.

Remember, these were comparisons of ISO 400 RAW files as exposed by the G3 and G9 in Av mode. The samples shown were not adjusted for levels, curves, saturation, sharpness, noise reduction, etc. The G9 samples were downsized to match the G3 samples. Obviously, each image could be improved with proper post processing.

My conclusion is that I’d prefer to use the G9 at ISO 400 instead of the G3 at ISO 400 – even though the G9 pixels are smaller.

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