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JPEG Image Size & Quality


Standard Test Scene

The PowerShot S50 allows you to select image size and JPEG quality separately. For image size you have the following options; RAW (2592 x 1944), 2592 x 1944 (L), 1600 x 1200 (M1), 1024 x 768 (M2) and 640 x 480 (S). For JPEG quality there are Super-Fine, Fine and Normal settings.

To give an impression of what some of the combinations of image size and quality produce the table below is a cross reference of some of them:

  • 2592 x 1944 RAW (converted to TIFF)
  • 2592 x 1944 Super-Fine JPEG
  • 2592 x 1944 Fine JPEG
  • 1600 x 1200 Super-Fine JPEG
  • 1024 x 768 Super-Fine JPEG
  • 640 x 480 Super-Fine JPEG

Images below are cropped 240 x 100 area of the image magnified 200% (nearest neighbour).


 
2048 x 1536
RAW
5,320 KB .CRW + .THM files (not available for download)
JPEG
Super
Fine

2,655 KB
JPEG
Fine

1,642 KB
 

 
1600 x 1200
JPEG
Super
Fine

1,140 KB
 

 
1024 x 768
JPEG
Super
Fine

482 KB
 

 
640 x 480
JPEG
Super
Fine

193 KB

Again, artifact free from the low compression 'Super-Fine' setting, with a default conversion there's very little difference between a RAW image and this high quality JPEG.

As I have commented previous Canon's low compression 'Super-Fine' setting provides artifact free JPEG's which would be difficult to distinguish from TIFF's of the same shot. You pay a larger storage penalty for these (although Compact Flash media is relatively cheap these days). To Canon's credit even the higher compression Fine setting has almost no visible artifacts.

As noted in previous PowerShot reviews Canon appear to use a high quality interpolation algorithm (probably bilinear) for their lower resolution images which means detailed clean images with no hard edges or alias effects.


Image Parameters

The S50 has a dedicated 'Effect' option on the FUNC menu. This provides five 'canned' photo effects (Vivid, Neutral, Low Sharpening, Sepia and B&W) as well as the 'Custom' option. Custom allows you to control three aspects of image processing (Contrast, Saturation and Sharpness).Although these settings are available in RAW mode they are not applied to the image in-camera but are stored in the RAW image header as the default settings for Canon's File Viewer Utility.

My only gripe must be that while it's good to see control over image processing I would have been much happier to see a greater latitude of adjustment, +/-3 levels at least.

Contrast and Saturation

Contrast -1 Contrast 0 Contrast +1
Saturation -1 Saturation 0 Saturation +1

Sharpness

Sharpness -1
Sharpness 0
Sharpness +1
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