Zoom
A typical 3x optical zoom range, with good performance.

37mm	111mm	4x Digital Zoom

The Canon SD900 zooms over the equivalent of a 37-111mm range, which is fairly typical for its class. Overall performance is quite good, with good detail and sharpness at wide angle. The 4x Precision Digital zoom takes it out to 12x total, with the typical loss of resolution associated with Digital Zoom, although the SD900 arguably does a better than average job.

Macro
A very small macro area, but noticeable blurring in the corners. Closest focusing distance is too close for the flash.

Standard Macro	Macro with Flash

The Canon SD900's macro setting captures a small minimum area of only 1.94 x 1.45 inches (49 x 37 millimeters). While the macro area is quite small, details are soft in the corners of the frame. Most cameras have some softening in the corners in macro mode (evidence of the optical characteristic "curvature of field").

The SD900's flash had trouble throttling down for the macro area and was partially blocked as well, resulting in a very uneven exposure. (Plan on using external lighting for any macro shots with the SD900.)

Distortion
Lower than average barrel distortion, slightly high pincushion.

Barrel distortion at 37mm is 0.47%

Pincushion at 111mm is 0.14%

This is the tendency for the lens to bend straight lines outward (like a barrel -- usually at wide angle) or inward (like a pincushion -- usually at telephoto). The SD900's 0.47% barrel distortion at wide angle is very low among the cameras we've tested, and not noticeable in most images. At the telephoto end, the SD900's 0.14% pincushion is lower than average, too.

Chromatic aberration
Moderate at wide angle (but small effect on images at edges; very little at telephoto).

Wide: moderate, top left @ 200%	Wide: moderately bright, top right @ 200%
Tele: still present, but dim in coloration, top left @200	Tele: still present, but dim in coloration, top right @200%

Chromatic aberration is low to moderate at wide angle, showing about 5-6 pixels of faint coloration on either side of the target lines, but decreases to very low levels at telephoto focal lengths. (This distortion is visible as a very slight colored fringe around the objects at the edges of the field of view on the resolution target.)

Corner Sharpness
Some softening in the corners of the frame, strongest effect in the lower right corner.

Wide: Soft in the lower right corner.	Wide: Sharp at the center.
Tele: Nearly equal in the lower right corner.	Tele: Sharp at the center.

The SD900 produced soft corners in a few shots, the lower right corner showing the most visible effect. Softening in the corners is very common with lenses on small cameras, and this is about average at wide angle.

Coverage
Optical viewfinder is tight and skewed to the top. Excellent accuracy from the LCD monitor.

37mm eq., optical viewfinder	111mm eq., optical viewfinder
37mm eq., LCD monitor	111mm eq., LCD monitor

The SD900's optical viewfinder was quite tight, showing only about 80% frame accuracy at both wide angle (79%) and telephoto (81%) lens settings. However, the LCD monitor showed at least 100% accuracy at both wide (104%) and telephoto (100%).