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Output image file quality / JPEG artifacts

Standard Test Scene

The PowerShot Pro1 has five selectable image sizes from the full native eight megapixel size (3264 x 2448) down to VGA. These sizes can be combined with any of three levels of JPEG compression (Super Fine, Fine or Normal). Additionally of course the Pro1 also supports RAW capture and writes a losslessly compressed Canon CRW file in this mode.

Below you will find crops of the same 240 x 180 portion of the center of a sequence of images taken at some of the available combinations of image size and quality. Crops shown are at 100%, saved as extremely high quality JPEG. The RAW file was converted to a TIFF using Canon ZoomBrowser EX 4.6 (supplied with the Pro1).

3264 x 2448 RAW (Lossless compression)
8,314 .CRW + 10 KB .THM (not for download)
3264 x 2448 JPEG Super Fine
3,828 KB (1.6:1 compression, 5 bpp)
3264 x 2448 JPEG Fine
2,406 KB (2.7:1 compression, 3 bpp)
3264 x 2448 JPEG Normal
1,088 KB (4:1 compression, 2 bpp)
2272 x 1704 JPEG Super Fine
2,023 KB (1.6:1 compression, 5 bpp)
1600 x 1200 JPEG Super Fine
1,021 KB (1.6:1 compression, 5 bpp)
1024 x 768 JPEG Super Fine
485 KB (1.6:1 compression, 5 bpp)
640 x 480 JPEG Super Fine
200 KB (1.6:1 compression, 5 bpp)

Canon's "Super Fine JPEG" mode uses such little compression that it's almost lossless, it is very hard to find any part of the image which exhibits any kind of JPEG artifact or loss of detail compared to a RAW converted image. That said the Fine compression more than adequate for most everyday shooting, again it would be hard to find any noticeable JPEG artifacts in this mode. It's good to see Canon using a decent interpolation algorithm for the downsampling carried out to create smaller size output images.

Color space

The Pro1 is the first non-SLR digital camera from Canon to provide selectable output color space. The 'Color space' menu option can be selected independently of the image parameter settings and provides a 'Standard' (sRGB) and 'Adobe RGB' option.

The Pro1 now uses the DCF 2.0 standard for naming Adobe RGB images, they begin with "_DSC" instead of the normal "DSC_". They are also now embedded with the Adobe RGB color profile, this means that color space aware applications such as Adobe Photoshop immediately recognize and apply the correct color profile.

GretagMacBeth ColorChecker samples

Place your mouse over the labels below the image to see the GretagMacbeth ColorChecker chart taken in each color space.

sRGB Adobe RGB *

* Note that the Adobe RGB image has been converted to the sRGB color space
for correct display on your web browser.

Test shot samples

Note that in these samples the Adobe RGB image has NOT been converted to sRGB and so to view it correctly you will have to load it into a color space aware photo application and assign the Adobe RGB color space. Below each sample is that image's CIE u'v' Color Distribution chart; larger gray triangle approximately represents the range of color which the human eye can resolve, the inner triangle the available gamut in each color space (sRGB or Adobe RGB).

sRGB Adobe RGB
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