Canon G1X Optics

Zoom
Very good optical performance from the 4x optical zoom.

The Canon PowerShot G1 X's 4x lens covers the equivalent of about 28-112mm zoom on a 35mm camera, compared to 28-140mm (5x) for the G12. Maximum aperture ranges from f/2.8 at wide-angle, to f/5.8 at telephoto. Sharpness is pretty good across most of the frame at full wide-angle and f/8, with some minor blurring in the corners, though very little chromatic aberration is visible. Some flare is evident around the bright white elements of this shot, though. At medium focal length (~56mm eq.), overall sharpness quite good across the frame, and flare isn't an issue. Results at full telephoto are also very good, with very good sharpness and minimal flare. Again, chromatic aberration is negligible because the G1 X suppresses it. The Canon G1 X's digital zoom (up to 4x) does a better than average job because of lower noise levels compared to most digicams, though we wouldn't recommend using higher magnifications due to the loss of fine detail that usually comes with strong digital enlargement.

Light Leak/Internal Lens Reflections

While shooting our Far-field ISO series, we noticed what looked to be internal lens reflections in high ISO shots, and we were able to replicate them in the lab. During our investigation, we determined the reflections are sensitive to focal length but do not depend on aperture or shutter speed. They are most apparent at around 50mm equivalent, and need a bright light or subject near the center or just below the frame. The reflections are quite noticeable at ISO 12,800, barely discernible at ISO 800 and all but invisible at lower ISOs. (Mouse over the ISO links above to compare thumbnails and crops. The crops above are from near the center of the image, but there's an even larger reflection in the center-right of the frame, and also some smaller ones near the top that are difficult to see. This lab image taken at ISO 12,800 shows where they are more clearly. For more details, click here.

Macro
A much larger than average macro area, with very good detail and resolution. Flash did well, but is partially blocked by the lens.

The Canon PowerShot G1 X's macro setting captured a much larger-than-average area of 8.79 x 6.59 inches (223 x 167 millimeters). Detail and resolution were both pretty good, and there's only minor softening in the extreme corners from field curvature of the lens. (Most cameras have some softening in the corners in macro mode. What we see here is better than average.) The Canon G1 X's flash did a good job throttling down, but the lens casts a shadow and flash coverage isn't even.

Distortion
Lower than average barrel distortion in JPEGs; very high at wide-angle in uncorrected RAW files.

JPEG: The Canon G1 X's just under 0.5% barrel distortion at wide-angle is actually fairly low compared to the average digital camera, especially considering its moderately wide 28mm equivalent focal length (see below for the explanation). The ~0.4% barrel distortion at the telephoto end is a bit higher than the average amount of pincushion distortion we normally see at telephoto, and is noticeable in some images. 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 DxO Optics Pro 7 with lens correction disabled, barrel distortion at wide-angle was much higher, at about 3.5%. Distortion at full telephoto is about the same as the in-camera JPEG, so no correction was performed by the camera at the telephoto end. Canon's bundled Digital Photo Professional software automatically reduces geometric distortion, producing distortion results very similar to in-camera JPEGs, though it stretches extreme corners a little more than the camera does.

We expect high distortion at wide-angle for smaller lenses though, so it's nothing to be overly concerned about unless you are using a RAW converter which does not understand the embedded "opcodes" to perform distortion corrections automatically. There is however going to be some loss of resolution and interpolation artifacts as a result of such strong correction, because pixels in the corners of the frame are being "stretched" to correct for the distortion. If you look closely at the corners in G1 X shots, detail is a little rough with normally straight edges in the resolution target looking jagged. Obviously, a lens that doesn't require such correction and is also sharp in the corners to begin with would be preferable, but relaxing constraints on distortion brings other benefits in the lens design, such as a compact, lower cost design.

Chromatic Aberration and Corner Softness
CA is low at wide-angle, and even lower at telephoto. Moderate blurring in the corners of the frame at wide-angle, but good corner sharpness at full telephoto.

Chromatic Aberration. Chromatic aberration is quite low at both wide-angle and full telephoto, because the G1 X's DIGIC 5 processor removes most of it. See below for examples of uncorrected C.A. 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 G1 X's lens produced moderately soft corners at full wide-angle when wide-open. Blurring was about the same in all for corners, but softness didn't extend very far into the frame, and the center was sharp. We suspect some of the blurring is due to the geometric distortion and CA correction taking place at wide-angle. Corners at full telephoto were pretty sharp but not quite as contrasty as the center. Vignetting was not a problem at either end of the zoom.

When the lens was stopped-down to f/8, corner sharpness improved at wide angle, though you can still see some softness and rough edges due to the distortion correction applied.

Chromatic Aberration Correction

As you can see, the Canon G1 X's DIGIC 5 processor does a great job suppressing most of the chromatic aberration in JPEGs (crops on the left) versus uncorrected RAW files (on the right). Canon's DPP software also suppresses CA similarly.

SLRgear-style Test Results. A lot of readers are no doubt interested in how the G1 X's lens performs at a number of focal lengths and apertures, so we ran the Canon G1 X through our SLRgear.com test suite:

Results here confirm pretty good, consistent optical performance across the focal length range.

Note that these results are not calibrated for accurate comparison to other cameras or lenses, and are only of value as a comparison from one aperture or focal length to another on the Canon G1 X. Also note that these results were obtained from camera JPEGs, so keep in mind that the distortion and chromatic aberration reduction the G1 X applies to JPEGs is reflected here.

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

The Canon PowerShot G1 X's optical viewfinder showed only about 73% coverage at wide-angle, and 74% coverage at full telephoto, and was shifted from the captured image (no parallax correction). The poor accuracy is no surprise for a non-TTL optical viewfinder, though. The LCD monitor had excellent accuracy, though, showing essentially 100% coverage at both wide-angle and full telephoto.