Canon S110 Optics

Zoom
A wider-than-average 5x optical zoom lens, with decent performance.

The Canon PowerShot S110's lens covers the equivalent focal range of about 24-120mm on a 35mm camera. The lens is pretty fast (f/2.0) at full wide angle, but maximum aperture drops off rather quickly to f/5.9 as you zoom to full telephoto. The following table reflects maximum aperture versus approximate equivalent focal length as reported by the camera:

Details are good but a little soft in the center of the frame at full wide angle (24mm eq.) and f/5.6, with some blurring and coma distortion in the extreme corners, though very little chromatic aberration is visible. Some flare is also evident around the bright white elements of this shot, though this image is a little overexposed which can exacerbate flare. At medium focal length (~50mm eq.), overall sharpness is slightly better, though extreme corners are still soft. Flare isn't as noticeable, though the exposure wasn't as bright as the wide-angle shot, so there aren't as many strong highlights. Results at full telephoto are similar with some minor corner softening, though the image is still a touch soft overall. Flare isn't as evident, and again, chromatic aberration is negligible. The Canon S110 also offers up to 4x digital zoom, though with the expected loss of fine detail that comes with digital magnification.

Macro
A slightly smaller than average macro area, with very good detail and resolution. Flash had some difficulty throttling down, and is partially blocked by lens.

The Canon PowerShot S110's macro setting captured a slightly smaller than average area of 1.73 x 1.30 inches (44 x 33 millimeters). Detail and sharpness are both pretty good across most of the frame, though there's some 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 S110's flash has some difficulty throttling down at this distance, causing overexposure where the flash wasn't blocked by the lens. The overexposure plus the shadow from the lens resulted in a very unevenly lit image. Plan on using external lighting for the closest macro shots with the S110.

Geometric Distortion
Higher than average barrel distortion at wide angle in JPEGs; very high at wide angle in Raw files. Low distortion at telephoto.

JPEG: The Canon S110's 1.1% barrel distortion at wide angle is higher than average and quite noticeable in some shots. At the telephoto end, the S110's less than 0.1% barrel distortion is a little unusual as we'd normally expect to see pincushion distortion at telephoto. The amount is quite low, though, at around 0.05%, which is barely noticeable. 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 is much higher, at about 4.6%. 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 (as does Adobe Camera Raw), producing distortion results very similar to in-camera JPEGs.

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 as well as possible 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. 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 very good corner sharpness at full telephoto.

Chromatic Aberration. Chromatic aberration is low to very low at both wide angle and full telephoto, because the Canon S110's DIGIC 5 processor removes most of it. See below of 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 S110's lens produces soft corners at full wide angle when wide open. Blurring is a little stronger in the top corners, but softness doesn't extend very far into the frame, and the center is quite sharp. Some of the blurring is due to the geometric distortion and CA correction taking place at wide angle, and you can see some interpolation artifacts in the corners at wide angle as well. All four corners at full telephoto are fairly sharp, as is the center.

Vignetting. Some very minor vignetting is noticeable at wide angle and telephoto at maximum aperture, as can be seen from the dimmer corner crops.

Stopped-down to f/5.6 at wide angle, corner sharpness improved but is still soft. At the telephoto end, maximum aperture is already quite small at f/5.9, and stopping down would start to lead to some diffraction related softness, so we didn't stop down any further. As you can see, vignetting also improved at wide angle.

CA Correction. Below are crops comparing in-camera JPEGs versus raw files converted with dcraw which doesn't correct for CA:

As you can see, CA is very high and bright at wide angle and moderate at telephoto in uncorrected raw files (crops on the right), so the S110's DIGIC 5 processor is doing a great job at suppressing most of the CA in JPEGs.

Overall, we'd say this is decent performance for a lens of its class, though corners are soft and distortion a little high at wide angle.

Coverage
Very good accuracy from the LCD monitor.

The Canon PowerShot S110's LCD monitor showed just under 100% coverage at wide angle, and just over 100% at telephoto. Very good results here.