JPEG Image Size & Quality

Standard Test Scene

The PowerShot S400 allows you to select image size and JPEG quality separately. For image size you have the following options; 2272 x 1704 (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 S400 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:

• 2272 x 1704 Super-Fine JPEG
• 2272 x 1704 Fine JPEG
• 2272 x 1704 Normal JPEG
• 1600 x 1200 Super-Fine JPEG
• 1024 x 768 Super-Fine JPEG

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

	2272 x 1704
JPEG Super Fine	1,895 KB
JPEG Fine	1,188 KB
JPEG Normal	548 KB
	1600 x 1200
JPEG Super Fine	1,025 KB
	1024 x 768
JPEG Super Fine	451 KB

The Super-Fine option provides a virtually artifact free JPEG image, while file sizes are on the large size it's a price worth paying for the superb quality output (and CF storage is relatively cheap). JPEG Fine does appear to soften the image slightly (some detail is lost) although it's hard to find visible JPEG artifacts. It's good to see that Canon are using a high quality interpolation algorithm when downsampling the full resolution image to lower resolutions. This provides very clean images without any jaggies or hard edges. It's also worth noting the conservative approach Canon take to sharpening, yet maintain detail.