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JPEG Image Size & Quality


Standard Test Scene

The PowerShot A70 allows you to select image size and JPEG quality separately. For image size you have the following options; 2048 x 1536 (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. Note that the A70 does not provide a RAW or TIFF output.

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:

  • 2048 x 1536 Super-Fine JPEG
  • 2048 x 1536 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
JPEG
Super
Fine

1,570 KB
JPEG
Fine

953 KB
 

 
1600 x 1200
JPEG
Super
Fine

987 KB
 

 
1024 x 768
JPEG
Super
Fine

476 KB
 

 
640 x 480
JPEG
Super
Fine

204 KB

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

Unfortunately the A70 doesn't provide direct control of image parameters such as contrast, saturation and sharpening. That's a pity considering the wide range of other controls available on this camera. Canon do provide five extra 'canned' photo effects which do allow you to at least have some options for adjustment.

Effects

Off (normal) Vivid (high color saturation) Neutral (low color saturation)
Low Sharpening Sepia B&W
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