Canon Powershot S20 Review
Enabling continuous mode on the S20 allows you to take a sequence of images by simply holding the shutter release button down. A quick preview of each frame is displayed while you shoot so you can (almost) frame each shot. The S20 allows you to shoot until the internal buffer is full (emptying and updating the small "dots" display in the bottom right corner of the LCD).
Shooting 640 x 480, NORMAL compression with the LCD OFF we managed 29 images at about 1.5fps, with the LCD ON this drops to about 1fps.
Stitch assist mode
Stitch assist mode of the S20 is especially good as it not only understands stitch shooting (panoramas) but displays previously shot images in a patchwork to allow you to align the next shot perfectly. I got good results using the S20 combined with Enroute's QuickStitch (NOT the supplied panorama software: PowerStitch which was pretty poor..).
JPEG Compression settings
Standard test scene
The S20 has three compression settings, Super-Fine, Fine and Normal. Super-Fine is a welcome addition to the normal range of settings and I would hope to see more digicam manufacturers following Canon's lead. The S20 doesn't feature an uncompressed mode, however Super-Fine mode is very low compression and very high quality JPEG, producing 1.4MB images which are immediately available for use (no importation or TWAIN drivers required here) but are at the same time indistinguishable in quality from a pure TIFF from other digicams. Excellent.
Below are three crops (blown up 200%) from samples taken at the three different compression settings.
|Super-Fine JPEG compression
No JPEG artifacts are visible, excellent detail and smooth flat areas.
|Fine JPEG compression
Some JPEG artifacts are visible.
|Normal JPEG compression
Fairly noticeable JPEG artifacts.
Here are the same cropped (blown up 200%) areas shot at 1024 x 768 and 640 x 480.
|1024 x 768 FINE
|640 x 480 FINE
"CCD Gain" / ISO sensitivity equiv.
The S20 features three possible ISO modes, 0 (ISO 100 equiv.), +1 (ISO 200 equiv.) and +2 (ISO 400 equiv.). This gives the S20 good flexibility to shoot in low light situations or where higher shutter speeds are required, one side effect of increasing the "Gain" (and this is true of all consumer digicams) is an increase in visible CCD noise which can be seen in the three crops (blown up to 200%) below.
(ISO 100) 1/20s @ F4.0
(ISO 200) 1/45s @ F5.0
(ISO 400) 1/90s @ F5.6