Canon G12 Optics

Zoom
A fairly wide, 5x optical zoom lens with very good performance.

The Canon PowerShot G12's lens remains the same as the G11's, covering the equivalent of a 28-140mm zoom on a 35mm camera with a maximum aperture range of f/2.8-4.5. The 5x optical zoom ratio is more than most consumer digital cameras offer, though not as much as the Nikon P7000's 28-200mm range. Results are quite good at wide-angle, with minimal blurring and coma distortion, though some minor to moderate chromatic aberration can be seen in the corners and edges, as well as some flare around the brighter areas of the scene. Results at full telephoto are also very good with strong detail across the frame and only small amounts of corner softness and chromatic aberration. The Canon G12's digital zoom does a pretty good job of maintaining fine detail despite the typical blurring and loss of resolution associated with digital zoom.

Macro
A very small macro area, with excellent detail and resolution in the center. Flash is mostly blocked by lens.

The Canon PowerShot G12's macro setting captured a smaller than average area of 1.22 x 0.92 inches (31 x 23 millimeters). Detail and resolution were both very good, though there's some softening in the corners that extends pretty far into the frame, as well as some moderate chromatic aberration. (Most cameras have some softening in the corners in macro mode.) The Canon G12's flash didn't work well at closest distance, as it was almost entirely blocked by the lens which resulted in a very dark, unevenly lit image. Plan on using external lighting for the closest macro shots with the G12.

Distortion
Slightly higher than average barrel distortion at wide-angle, almost no distortion at telephoto.

JPEG: The Canon G12's 0.9% barrel distortion at wide-angle is slightly higher than average and is noticeable in some shots. At the telephoto end, the G12's distortion is negligible, less than one pixel's worth. 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).

Raw: When converting RAW files using dcraw (which doesn't apply any distortion correction), barrel distortion at wide-angle and telephoto looks to be the same as the JPEGs, so the G12 is not correcting for lens distortion in its JPEGs (unlike the S95).

Chromatic Aberration and Corner Softness
C.A. is moderately high at wide-angle, and mild at telephoto. Mild to moderate blurring in the corners of the frame at wide-angle at maximum aperture, but good corner sharpness at telephoto.

Chromatic Aberration. Chromatic aberration is moderately high at wide-angle. The color fringing is bright and extends fairly deep into the frame, but the width and intensity of the fringes reduce as you move toward the center. At telephoto, chromatic aberration is much lower and therefore less noticeable. As mentioned previously, dcraw doesn't fully support the G12's files yet (it doesn't interpolate color correctly), and other converters tend to apply some correction automatically, so it's difficult to tell if the Canon G12 is applying some correction for C.A. in its JPEGs. We suspect not, given JPEG levels. Chromatic aberration is a type of distortion visible as a slight colored fringe around the objects at the edges of the field of view on the resolution target.

Corner Softness. The Canon G12's lens produced mild to moderate corner softness at full wide-angle. Blurring was stronger in the left corners with the bottom left being the softest, but softness didn't extend very far into the frame. The right corners were sharp, as was the center. All four corners at full telephoto were only slightly soft. The center was fairly sharp, though as is often the case, contrast is a touch lower than at wide-angle. Overall results are pretty good, especially considering that these shots were taken at maximum aperture. That's because corner sharpness generally improves as the lens is stopped down to smaller apertures.

Here are the same corners at f/5.6, showing less blurring and C.A. compared to wide-open, especially at wide-angle:

Coverage
Very poor accuracy from the optical viewfinder, but excellent accuracy from the LCD monitor.

The Canon PowerShot G12's optical viewfinder showed about 78% coverage at wide-angle, and 79% coverage at full telephoto. The poor accuracy is no surprise for a non-TTL optical viewfinder, though. The LCD monitor had excellent accuracy, showing essentially 100% coverage at both wide-angle and full telephoto.