Zoom
Very good performance with the 4x optical zoom lens. Digital zoom also performs fairly well.

35mm	140mm	4x Digital Zoom

The Canon PowerShot A550's optical zoom covers the equivalent of a 35-140mm range, which is slightly greater than most average digital cameras. Results were quite good at wide angle, with minimal blurring in the corners and low coma distortion in the tree branches against the sky. The camera's 4x digital zoom also performs pretty well, with tolerable losses in resolution and quality from the digital enlargement. Still, digital zoom is never a good substitute for true optical zoom.

Macro
A small macro area with excellent detail and high resolution. Flash exposure was not usable up close.

Standard Macro	Macro with Flash

The Canon A550's macro setting performed quite well, capturing a very small minimum area of 1.98 x 1.48 inches (50 x 38 millimeters). Detail and resolution were both excellent, though there's a moderate amount of softening in the corners from the lens. (Most cameras have some softening in the corners in macro mode.) The flash blew out most of the exposure, with a strong shadow in the lower right corner of the frame from the lens. Plan on using external lighting for the best results with the A550's macro setting.

Distortion
Moderate barrel distortion, though very low pincushion.

Barrel distortion at 35mm is 0.7%

Pincushion at 140mm is less than 0.1%

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 Canon PowerShot A550's 0.7% barrel distortion at wide angle is just a little less than average among the cameras we've tested, although still quite noticeable in its images. At the telephoto end, the A550's pincushion distortion was quite low at less than 0.1%, and had little effect.

Chromatic aberration
Moderate, only slightly noticeable effect on images at edges.

Wide: Moderately high and bright, top left @ 200%	Wide: Higher and broader, top right @ 200%
Tele: Low, top left @200%	Tele: Low, top right @200%

Chromatic aberration is moderately high at wide angle, showing about 6-7 pixels of bright coloration on either side of the target lines. (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.) The effect is much stronger on the right side of the frame, though the aberration is increased by some blurring in the corner here. At telephoto, aberration is much lower, though again stronger on the right side of the frame. Overall, the effect is only slightly noticeable in most of our test shots.

Corner Sharpness
Strong blurring in the right corners of the frame at wide angle, though less blurring at telephoto.

Wide: Very soft in the right corners.	Wide: Sharp at center
Tele: Only slightly soft in the corners (upper right)	Tele: Still slightly soft at center

The Canon PowerShot A550 produced very soft corners in the right side of the frame at full wide angle, with minimal blurring on the left. At full telephoto, there's only slight blurring in the corners of the frame, with very little effect on resulting images.

Coverage
Excellent accuracy from the LCD monitor, though the optical viewfinder proved a bit tight.

35mm eq., Optical	140mm eq., Optical
35mm eq., LCD	140mm eq., LCD

The Canon PowerShot A550's optical viewfinder was a bit tight, showing approximately 83% frame accuracy at wide angle, and about 81% at telephoto. However, the camera's LCD monitor showed right about 100% accuracy at both zoom settings.