Canon SL1 Optics

Zoom
The Canon EF-S 18-55mm IS STM lens offers a typical zoom range , with decent performance for its class.

The Canon EF-S 18-55mm f/3.5-5.6 IS STM kit lens offers a typical optical zoom range of about 3.1x, with a 35mm-equivalent range of about 29-88mm. Sharpness and contrast are pretty good across much of the frame at 18mm and f/8, however there's moderate chromatic aberration and some minor softness visible in the corners, as well as some minor flare around bright objects. Results at full telephoto are also good at f/8, with good sharpness and contrast across much of the frame, as well as lower levels of chromatic aberration, though corners look to be a touch soft. Above average performance far-field for an inexpensive kit lens, and the built-in image stabilization will come in hand for low-light shots. (These shots are meant mainly to illustrate zoom ratio and are not ideal for judging optical performance; see below for how the lens performed in the lab.)

Macro
A small macro area (for an SLR kit lens), with very good detail. Flash throttled down well.

The Canon EOS Rebel SL1's macro performance will of course depend entirely on the lens in use. With the 18-55mm STM lens set to 55mm, the Canon Rebel SL1 captured a smaller-than-average size minimum area for an SLR kit lens, measuring 2.25 x 1.50 inches (57 x 38 millimeters). Details are quite strong in the center of the frame, though corners are quite soft. (Most lenses have some softening in the corners at macro distances, though.) The Canon SL1's flash throttled down well, producing a good, even exposure with no detectable shadow from the lens barrel.

Geometric Distortion
Higher than average barrel distortion at wide angle but low pincushion distortion at telephoto with the 18-55mm STM kit lens.

The Canon EF-S 18-55mm STM lens produced images with about 0.9 percent barrel distortion at wide angle, which is higher than average and noticeable in some shots. At the telephoto end, there was less than 0.1% pincushion distortion, which is negligible The Canon SL1 does not correct for geometric distortion in its JPEGs, as uncorrected RAW files have identical amounts. Geometric Distortion 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 and Corner Sharpness
Moderate to high chromatic aberration in the corners with the 18-55mm STM lens. The lens produces soft corners at wide angle.

Chromatic Aberration. Chromatic aberration in the corners with the Canon 18-55mm STM lens is high and bright at wide angle (18mm) but only moderate at full telephoto (55mm). The amount and intensity of the color fringing reduces as you move toward the center of the image, to the point where it is very low at the center. See below for how well the Canon SL1's optional chromatic aberration correction works.

Corner Softness. The 18-55mm STM lens produced some soft corners when wide-open at maximum aperture. At full wide angle, the bottom right corner is pretty soft, though blurring doesn't extend very far into the frame. The other three corners are pretty sharp, though, and the center is quite sharp. At full telephoto, the top left corner is softest and the bottom right is sharp, while sharpness in the other corners is somewhere between. The lens is quite sharp in the center.

Vignetting. Vignetting or corner shading is not an issue in the above crops, but that's because the Canon SL1's Peripheral Illumination Correction is enabled by default. See below for comparisons with it off.

f/8: Chromatic aberration in the corners is still moderate to high, while sharpness in the corners improves slightly when stopped down to f/8, though the same corners are still softer than the center, particularly at wide angle. As you can see, the Canon SL1's Peripheral Illumination Correction over-corrected at wide angle, producing a noticeably brighter corner crop than the center.

Chromatic Aberration Correction
The Rebel SL1 offers optional Chromatic Aberration Correction to reduce lateral C.A. with Canon lenses.

As you can see, the Canon SL1's Chromatic Aberration Correction feature was very effective at removing almost all the lateral chromatic aberration in our 18-55mm STM lens test shots above.

Overall, a better-than-average performance for an inexpensive kit lens.

Peripheral Illumination Correction
Like most recent Canon DSLRs, the SL1 features Peripheral Illumination Correction feature to reduce vignetting or lens shading with Canon lenses.

Like most Canon DSLRs, the SL1 provides what the company calls "Lens Peripheral Illumination Correction," which corrects for lens shading (commonly called "vignetting"), attempting to produce a more uniform exposure across the frame by compensating for the light fall-off seen with some lenses in the corners of the frame. Mouse over the Off and On links above to see the effect on the 18-55mm kit lens at wide-angle and telephoto at maximum aperture. PIC is enabled by default.

Peripheral Illumination Correction and Chromatic Aberration Correction are supported for over 85 different Canon lens models, in both raw and JPEG workflows. For JPEG shooting, the correction is made at capture time, while raw shooters can access the function in Canon's Digital Photo Professional software. From the factory, the SL1 body ships with correction data for about 25 lens models. Canon's EOS Utility software allows correction data for lenses (including models as-yet unreleased) to be uploaded to the Canon SL1.

Accuracy
Average accuracy from the optical viewfinder, very good accuracy from the LCD in Live View mode.

Testing with a low-distortion mid-focal length macro lens to minimize the effects of lens distortion, we measured the Canon SL1's optical viewfinder's coverage at close to 96%. This is better than Canon's 95% specification, but the image is offset both vertically and horizontally with respect to the sensor, which is unfortunately quite common with optical viewfinders in consumer-oriented models (and many prosumer models). Live View mode using the LCD is much more accurate, resulting in just over 100% coverage (a little loose), and of course the image isn't offset.