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JPEG/TIFF Image Size & Quality

The G1 has no less than ten different resolution / size combinations. You can choose from 2048 x 1536, 1024 x 768 and 640 x 480 as the image resolution, saving as JPEG you can choose from compression settings of Super-Fine, Fine and Normal additionally there's the lossless RAW format which only shoots at 2048 x 1536.

Standard Test Scene

To give an impression of what each combination of image size and quality produces the table below is a cross reference of image size against quality with an original image available for each, all images were shot within seconds of each other of the same subject. We've resaved the RAW shot as a TIFF for the purists out there who want to see what a RAW file would look like up-close, we've not made the RAW file itself (.CRW) publicly available as you can't open it without the new TWAIN driver which comes with the G1 (or EOS-D30). We may well publish this later.

Images below are 100% cropped 480 x 200 area of the image.


 
2048 x 1536
RAW
Resaved as 5,989 KB LZW 8-bit TIFF
SUPER
FINE

1,917 KB
FINE
1,056 KB
NORM
512 KB
 

 
1024 x 768
SUPER
FINE

315 KB
FINE
315 KB
NORM
315 KB
 

 
640 x 480
SUPER
FINE

315 KB
FINE
315 KB
NORM
315 KB

So, is there much difference between Super-Fine and RAW? Well, if you simply import the RAW files as is (using the camera settings) it'll be extremely difficult to see any difference between Canon's excellent Super-Fine JPEG (very light compression) and RAW. However, RAW provides lots of flexibility you can't get out of JPEG, you can alter the white balance, contrast, sharpening or saturation settings before importing, something impossible with JPEG. That's because the RAW files are simply that, raw data which has come directly from the camera's imager (CCD) before any in-camera processing has taken place, this can be seen as the true "digital negative".

More on RAW files later in this review...


ISO (Sensitivity) Adjustment

ISO equivalence on a digital camera is the ability to increase the sensitivity of the CCD to allow for faster shutter speeds and/or better performance in low light. The way this works in a digital camera is by "turning up the volume" on the CCD's signal amplifiers, nothing is without its price however and doing so also amplifies any noise that may be present and often affects colour saturation.

Interestingly the G1 is the first of the current crop of 3 megapixel digital cameras which has a slow ISO of 50, this slower ISO should in theory provide cleaner (less noisy) images in well lit situations and enable the use of large apertures (small F number) in even very brightly lit situations. Below are three images, in order ISO 50, 100, 200 and 400.

ISO 50, 1/13s, F5.6
ISO 100, 1/25s, F5.6
ISO 200, 1/50s, F5.6
ISO 400, 1/100s, F5.6

Almost identical noise at ISO 200 and 400 as we've found on other 3 megapixel digital cameras. But I think the addition of the ISO 50 setting is definitely worthwhile, at ISO 100 there's some blotchy red/blue noise in the shadow, at ISO 50 it's smooth and clean making ISO 50 an obvious choice for those really important / well lit shots. It's also worth noting that you can set up the G1 to use ISO 50 out of preference, Auto ISO will use ISO sensitivities between 50 and 100 which means you'll get the best quality if you have good light.

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