Canon SD850 IS Optics

Zoom
Very nice performance with the 4x zoom lens, and pretty good results with digital zoom as well.

The Canon PowerShot SD850 IS features an optical zoom covering the equivalent of a 35-140mm range, slightly better than the average consumer digital camera. Some corner softness and coma distortion were present at full wide angle, but overall results were still good, with fairly sharp details. The camera's 4x digital zoom did a pretty good job, despite the fuzzy details in the finer areas. Though resolution and quality are compromised, results actually aren't too bad for digital enlargement.

Macro
A very tiny macro area with excellent detail and high resolution. Flash exposure was very uneven up close though.

The Canon PowerShot SD850 IS's macro setting performed well, capturing a very small minimum area of 1.17 x 0.87 inches (30 x 22 millimeters). Detail and resolution were both excellent though, with a moderate amount of softening in the corners from the lens. (Most cameras have some softening in the corners in macro mode, but the SD850 IS actually performs pretty well here.) At such close shooting range, the SD850 IS' flash is practically useless, as it's mostly blocked by the lens. (Plan on using external lighting with your closest shots.)

Distortion
Moderate barrel distortion at wide angle, but practically no distortion at telephoto.

The Canon PowerShot SD850 IS's 0.8% barrel distortion at wide angle is about average among the cameras we've tested, although still uncomfortably high. At the telephoto end, the SD850 IS actually produced a tiny amount of barrel distortion, about one pixel, 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).

Chromatic aberration
High, very noticeable effect on images at edges, but extends only a short way into the frame.

Chromatic aberration is rather high at both wide angle and telephoto, showing 10+ pixels of very 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 pretty noticeable in several of our test shots, but the good news is that it doesn't extend very far into the frame.

Corner Sharpness
Strong blurring in the corners at wide angle, though better performance at telephoto. Worst blurring is restricted to the very corners though.

Our sample of the Canon PowerShot SD850 IS produced very soft corners at wide angle, with the strongest effect in the right corners. However, at telephoto, blurring was minimal in the corners compared to the center of the frame, and even at wide angle, the blurring didn't extend very far into the picture.

Coverage
Good accuracy with the LCD monitor, but poor results with the optical viewfinder.

The Canon PowerShot SD850 IS's optical viewfinder fell short in terms of frame accuracy, showing only 78% accuracy at wide angle and about 77% at telephoto. The resulting image was also slanted quite markedly toward the lower left corner. The camera's LCD monitor produced much better results, showing about 100%+ frame accuracy at both zoom positions.