Canon SL1 Image Quality
Saturation & Hue Accuracy
Very good saturation and excellent hue accuracy.
|In the diagram above, the squares show the original color, and the circles show the color that the camera captured. More saturated colors are located toward the periphery of the graph. Hue changes as you travel around the center. Thus, hue-accurate, highly saturated colors appear as lines radiating from the center. Mouse over the links above to compare ISOs, and click to load a larger version.|
Skin tones. The Canon SL1 produced pleasing, natural-looking Caucasian skin tones in our tests when using both manual and auto white balance settings. Darker skin tones show a small nudge toward orange, but good results overall. Where oversaturation is most problematic is on Caucasian skin tones, as it's very easy for these "memory colors" to be seen as too bright, too pink, too yellow, etc.
Hue. The Canon Rebel SL1's hue accuracy is excellent, much better than average. There are the usual shifts in cyan toward blue (actually quite small), red toward orange, and orange toward yellow, but all are fairly minor. (The cyan to blue shift is very common among the digital cameras we test; we think it's a deliberate choice by camera engineers to produce better-looking sky colors.) Average "delta-C" color error at base ISO is only 3.3, which is outstanding, one of the best scores we've recorded to date. Delta-C color error increases with ISO, but remains better than average even at the highest ISO. Hue is "what color" the
The Canon EOS Rebel SL1 offers a total of nine saturation settings, four above and four below the default saturation. This covers a very wide range of saturation levels, and as it should, the Canon SL1's saturation adjustment affects only saturation, leaving the contrast of images more or less unaltered. (In some cameras, saturation tends to affect contrast, and vice versa.) The fine steps between settings mean you can program the camera to just the level of saturation you prefer. As usual for Canon, well done.
|Saturation Adjustment Examples|
The table above shows alternate settings including the default as well as the two extreme saturation settings. Click on any thumbnail above, then click again to see the full-sized image.
| See full set of test images
See thumbnails of all test and gallery images
Exposure and White Balance
Indoors, incandescent lighting
Auto and Incandescent settings both struggled with household incandescent lighting, though Manual white balance worked well. Slightly higher than average exposure compensation required.
|Auto White Balance
|Incandescent White Balance
|Manual White Balance
Indoors, under incandescent lighting, the Canon EOS Rebel SL1's Auto and Incandescent white balance settings struggled, both producing very warm red/orange color casts. Unfortunately, this is common among cameras we've tested, but disappointing nonetheless. The Manual setting produced the most accurate results, though just slightly cool overall. The Rebel SL1 doesn't offer a Kelvin temperature setting like its more expensive siblings, but like all recent Canon SLRs, you can shift color balance toward more or less green vs magenta or blue vs amber, using a +/-9 step grid format display. The Canon Rebel SL1 required +0.7 EV exposure compensation for this shot, which is slightly higher than the +0.3 EV average among the cameras we've tested. (Our test lighting for this shot is a mixture of 60 and 100 watt household incandescent bulbs, a pretty yellow light source, but a very common one in typical home settings here in the U.S.)
Color and saturation are very good, though a tendency towards slightly cool color balance and slightly high contrast under harsh lighting. Slightly below average exposure accuracy.
|Auto White Balance,
|Auto White Balance,
Outdoors, the Canon EOS Rebel SL1 tended toward a slightly cool color balance, though overall color was generally very good. The Canon Rebel SL1 required +1.0 EV exposure compensation to keep the mannequin's face bright, a little more than the typical +0.7 EV we're accustomed to using for our "Sunlit" portrait shot. The Canon SL1's default contrast is a little high, producing some washed-out highlights and dark shadows under the deliberately harsh lighting of our "Sunlit" portrait test shown above left, though the camera's contrast, Auto Lighting Optimizer and Highlight Tone Priority settings do help with high contrast scenes like these. See below for examples of this. The Far-field shot (above right) was also a touch cool, and exposure a bit dim, though the camera did a good job of avoiding blown highlights at default exposure. Deep shadows however are quite dark and somewhat noisy.
Very high resolution, ~ 2,100 lines of strong detail from JPEGs, about 2,300 from RAW.
|Strong detail to
2,100 lines horizontal
|Strong detail to
2,100 lines vertical
|Strong detail to
2,300 lines horizontal
ACR Converted RAW
|Strong detail to
2,300 lines vertical
ACR Converted RAW
Our laboratory resolution chart showed the Canon Rebel SL1's images with sharp, distinct line patterns down to about 2,100 lines per picture height horizontally and about the same vertically. Some may argue for higher numbers, but aliasing and sharpening artifacts start to interfere at this resolution. Extinction of the pattern occurred just past 3,200 lines horizontally and at about 3,000 lines vertically. Adobe Camera Raw converted .CR2 files show higher resolution than the in-camera JPEG, perhaps another 200 lines, and complete extinction of the pattern was extended well past 3,200 lines in the horizontal direction, and to about 3,200 lines in the vertical direction. While ACR was able to extract more detail, it also produced more moiré and false colors, especially in vertical lines. Use these numbers to compare with other cameras of similar resolution, or use them to see just what higher resolution can mean in terms of potential detail.
Sharpness & Detail
Good sharpness and loads of detail with a sharp lens. Some minor detail loss to noise reduction processing even at low ISOs.
|With default sharpening settings, the
Canon Rebel SL1's JPEG files show some minor sharpening artifacts.
|Subtle detail: Hair
Noise suppression blurs
detail in areas of subtle contrast,
as in the darker parts of
the model's hair here.
Sharpness. The Canon EOS Rebel SL1's 18-megapixel sensor captures excellent image detail when coupled with a good lens, though some minor edge-enhancement artifacts are visible around high-contrast edges, as shown in the crop above left. (The above left crop shot was taken with Canon's very sharp 16-35mm f/2.8L II USM lens at f/8.) Edge enhancement creates the illusion of sharpness by enhancing colors and tones right at the edge of a rapid transition in color or tone.
Detail. The crop above right shows some detail loss due to noise suppression in darker areas and in areas with low contrast, but no more than we're accustomed to seeing at these resolutions. Good performance for an 18-megapixel APS-C sensor. (The image above right of the hair was taken with our very sharp Sigma 70mm f/2.8 reference lens.) Noise-suppression systems in digital cameras tend to flatten-out detail in areas of subtle contrast. The effects can often be seen in shots of human hair, where the individual strands are lost and an almost "watercolor" look appears.
Raw vs In-Camera JPEGs
As mentioned above, the Canon SL1 does an excellent job of capturing sharp, detailed JPEGs when coupled with a sharp lens, but as is usually the case, additional detail can be extracted by carefully processing its RAW files.
In the table above, mousing over a link at the bottom will load the corresponding crop in the area above, and clicking on the link will load the full resolution file. Examples include in-camera Fine JPEG, the matching RAW file processed through Canon's Digital Photo Professional (DPP) software using default settings, and finally, the same RAW file processed through Adobe Camera Raw (ACR 8.1), then sharpened in Photoshop using 300% unsharp masking with an 0.3 pixel radius.
Canon's DPP software produced images similar to in-camera JPEGs, perhaps with just slightly better detail. Images processed through ACR show an improvement in fine detail compared to the DPP conversions, but also show a bit more noise at default settings, which is not unusual. You may want to experiment with ACR's noise reduction settings to find the detail versus noise trade-off you're looking for. Regardless, the Canon SL1 is clearly a camera that carries a lot of detail in its RAW files.
ISO & Noise Performance
Very good detail versus noise up to ISO 1,600, though detail suffers at higher ISOs.
Default High ISO Noise Reduction
|ISO 100||ISO 200||ISO 400|
|ISO 800||ISO 1,600||ISO 3,200|
|ISO 6,400||ISO 12,800||ISO 25,600|
The Canon SL1's high ISO performance is pretty good, very similar to the Canon T4i's. Images are quite clean at ISOs 100 through 400, with just a tiny amount of luminance noise seen in the shadows, as well as what looks to be chroma noise in the darker strands of hair. Noise "grain" is slightly more evident at ISO 800, but detail remains very strong despite some minor blurring due to noise reduction. ISO 1,600 is of course noisier, but fine detail is still very good. At ISO 3,200 noise grain becomes coarser, blurring stronger and chroma noise more apparent, resulting in a more noticeable drop in detail. ISO 6,400 is quite grainy with obvious chroma noise, but there is still some fine detail left. Noise and the effects of noise reduction working hard to keep it under control really become apparent at ISO 12,800 and especially 25,600, with strong blurring and obvious chroma blotching, along with a drop in saturation.
There are also what look to be demosaicing errors in areas of fine vertical detail and high local contrast, such as the horizontal bands in the strands of hair on the mannequins's forehead at lower ISOs (see ISO 100 crop at right). We've seen these artifacts in our indoor portrait JPEG images from other Canon SLRs, as well as hints of them in JPEGs from other manufacturers, so they're not that unusual. The aberrations are very subtle to be sure, but they're something to be aware of if you plan to make very large prints of similar subject matter from JPEGs. They don't appear in RAW files processed with a good converter such as Adobe Camera Raw.
Overall though, a very good performance for an entry-level model, similar to the Canon T4i's. See the Print Quality section below for our evaluation of maximum print sizes at each ISO setting.
A note about focus for this shot: We shoot this image at f/4, using one of three very sharp reference lenses (70mm Sigma f/2.8 macro for most cameras, 60mm f/2.8 Nikkor macro for Nikon bodies without a drive motor, and Olympus Zuiko 50mm f/2.0 for Four Thirds and Micro Four Thirds bodies). To insure that the hair detail we use for making critical judgements about camera noise processing and detail rendering is in sharp focus at the relatively wide aperture we're shooting at, the focus target at the center of the scene is on a movable stand. This lets us compensate for front- or back-focus by different camera bodies, even those that lack micro-focus adjustments. This does mean, though, that the focus target itself may appear soft or slightly out of focus for bodies that front- or back-focused with the reference lens. If you click to view the full-size image for one of these shots and notice that the focus target is fuzzy, you don't need to email and tell us about it; we already know it. :-) The focus target position will simply have been adjusted to insure that the rest of the scene is focused properly.
Extremes: Sunlit, dynamic range and low light tests
Very high resolution with strong overall detail, but somewhat high default contrast and unremarkable dynamic range. Highlight Tone Priority and contrast adjustment options do a great job of dealing with tough lighting. Good low-light performance, but autofocus can struggle.
|+0.3 EV||+0.7 EV||+1.0 EV|
The Canon EOS Rebel SL1 produced moderately high contrast with some washed-out highlights and deep shadows under the deliberately harsh lighting of the test above. The mannequin's face was too dim at the +0.3 EV and +0.7 EV settings, so we preferred the image with +1.0 EV exposure compensation. This resulted in more clipped highlights in the shirt and flowers than we're used to seeing from an APS-C sensor lately, indicating mediocre dynamic range compared to the best of recent competitors. Shadow detail was however pretty good, though somewhat noisy. Bottom line: while dynamic range isn't bad, the Canon SL1 struggled a bit with this difficult shot compared to recent state-of-the-art peers.
Because digital cameras are more like slide film than negative film (in that they tend to have a more limited tonal range), we test them in the harshest situations to see how they handle scenes with bright highlights and dark shadows, as well as what kind of sensitivity they have in low light. The shot above is designed to mimic the very harsh, contrasty effect of direct noonday sunlight, a very tough challenge for most digital cameras. (You can read details of this test here. In actual shooting conditions, be sure to use fill flash in situations like the one shown here; it's better to shoot in open shade whenever possible.)
We really like it when a camera gives us the ability to adjust contrast and saturation to our liking. It's even better when those adjustments cover a useful range, in steps small enough to allow for precise tweaks. As was the case with its saturation adjustment, the Canon SL1's contrast setting meets both challenges very well.
|Contrast set to lowest,
|Contrast set to lowest,
At its lowest contrast setting, the Canon SL1 did an excellent job of preserving highlight detail, maintaining fairly natural-looking skin tones, and holding nice detail in the shadows. Overall, very good results here when the contrast setting is adjusted.
|Contrast Adjustment Examples|
The Canon Rebel SL1's contrast-adjustment control offers a very broad range of control in usefully fine gradations, and does a good job of adjusting contrast without affecting color saturation in the process. (As noted earlier regarding saturation adjustment, something that not all cameras manage to do.)
Highlight Tone Priority
The Canon EOS Rebel SL1's Highlight Tone Priority (HTP) option did an excellent job of preserving highlight detail, as shown below. (Mouse over the Off and On links to load the corresponding thumbnail, histogram and crops.)
Both shots above were captured at the same exposure, the only difference being that HTP was enabled for the second shot which necessarily increases the ISO to 200; part of how HTP works. The result is evident in the histograms and thumbnails above, clearly showing the superior highlight preservation when HTP is enabled, while shadow brightness is left relatively untouched. If you look closely at shadows however, you'll notice an increase in noise is the price you pay when ISO is boosted from 100 to 200. Except in the very deepest shadows, though, overall noise is low enough at ISO 200 that this is really a negligible trade-off for all but the most critical applications.
Automatic Lighting Optimization
Like previous EOS models, the Canon SL1 offers three selectable levels of Automatic Lighting Optimization (ALO), plus Off. In fully automatic and Creative Auto exposure modes, ALO is automatically enabled. All four shots below were taken with the same default exposure settings. Mouse over the links below to load the associated thumbnail and histogram, and click on the links to load full resolution images.
As you can see above, ALO has the effect of shifting shadows and mid-tones in the histograms to the right, brightening shadows and indeed most of the image without clipping too many additional highlights. ISO is not boosted for ALO so increased noise is not an issue, though it may be slightly more visible in shadows that have been boosted significantly.
Just like most point & shoot cameras these days, the Canon EOS Rebel SL1 has the ability to detect faces in Live View mode, and adjust exposure and focus accordingly.
Face Detect: Off
Face Detect: On
As you can see from the examples above, it works well, as the center image with face detection enabled is much better exposed for the face (actually slightly overexposed) than the left image where face detection was not employed. Full Auto mode (right) was also an improvement over Aperture Priority without face detection, selecting a larger aperture than we normally use for this shot (f/4 vs f/8), though the mannequin's face is still somewhat dim.
A key parameter in a digital camera is its Dynamic Range, the range of brightness that can be faithfully recorded. At the upper end of the tonal scale, dynamic range is dictated by the point at which the RGB data "saturates" at values of 255, 255, 255. At the lower end of the tonal scale, dynamic range is determined by the point at which there ceases to be any useful difference between adjacent tonal steps. Note the use of the qualifier "useful" in there: While it's tempting to evaluate dynamic range as the maximum number of tonal steps that can be discerned at all, that measure of dynamic range has very little relevance to real-world photography. What we care about as photographers is how much detail we can pull out of the shadows before image noise becomes too objectionable. This, of course, is a very subjective matter, and will vary with the application and even the subject matter in question. (Noise will be much more visible in subjects with large areas of flat tints and subtle shading than it would in subjects with strong, highly contrasting surface texture.)
What makes most sense then, is to specify useful dynamic range in terms of the point at which image noise reaches some agreed-upon threshold. To this end, Imatest computes a number of different dynamic range measurements, based on a variety of image noise thresholds. The noise thresholds are specified in terms of f-stops of equivalent luminance variation in the final image file, and dynamic range is computed for noise thresholds of 1.0 (low image quality), 0.5 (medium image quality), 0.25 (medium-high image quality) and 0.1 (high image quality). For most photographers and most applications, the noise thresholds of 0.5 and 0.25 f-stops are probably the most relevant to the production of acceptable-quality finished images, but many noise-sensitive shooters will insist on the 0.1 f-stop limit for their most critical work.
JPEG. The graph at right (click for a larger version) was generated using Imatest's dynamic range analysis for an in-camera Canon Rebel SL1 JPEG file with a nominally-exposed density step target (Stouffer 4110). At default camera settings and base ISO, the graph shows 12.2 f-stops of total dynamic range, with 7.42 f-stops at the "High" Quality level. These are decent numbers for a JPEG, though somewhat lower than some recent competitors. Compared to the Canon T4i which uses a similar sensor, the SL1 scored essentially the same at the High Quality level (7.42 vs 7.41 f-stops), and significantly higher in total dynamic range (12.1 vs 11.1 f-stops), though as mentioned above, the total dynamic range number is not terribly useful. Note though that this measurement has a margin of error of about 1/3 f-stop, so differences of less than 0.33 can be ignored.
RAW. The graph at right is from the same Stouffer 4110 stepchart image captured as a RAW (.CR2) file, processed with Adobe Camera Raw using the Auto setting, then tweaking from there. The Canon SL1's RAW file scored 0.4 f-stop more in total dynamic range (12.6 vs 12.2 f-stops) but the score at the highest quality level increased only 0.19 f-stops from 7.41 to 7.56, which is an insignificant improvement and below average these days. Results are very similar to those of the Canon T4i at the High Quality level (7.61 vs 7.35 f-stops), though the total dynamic range score was higher like the JPEG, at 12.6 vs 11.9 f-stops. The score at the "Low" setting which is what most sites that report dynamic range seem to measure is essentially the same as the T4i's, at 11 versus 11.1 f-stops. Like all recent Canon SLRs, these scores are somewhat below average for a modern APS-C sensor. As always, it's worth noting here is that ACR's default noise reduction settings reduced overall noise somewhat (see the plot in the lower left-hand corner) relative to the levels in the in-camera JPEG, which would tend to boost the dynamic range numbers for the High Quality threshold, but notice that pixel noise in darker midtones and shadows is actually higher than the JPEG. Also, the extreme highlight recovery being performed by ACR here would likely produce color errors in strong highlights of natural subjects.
Low Light. The Canon SL1 performed well on the low-light test, capturing bright images at the lowest light level (1/16 foot-candle), even with the lowest sensitivity setting (ISO 100). As expected, noise increases as ISO goes up and light levels go down, but noise remains fairly low up to ISO 1,600, and performance is still quite good up to ISO 6,400. Noise is a little high at ISOs 12,800 and 25,600, particularly when noise reduction is minimized (extreme right column in the table above), though that's to be expected.
We noticed a few hot pixels here and there particularly when long exposure noise reduction was turned off (where they can be expected), but that's not unusual. And we didn't see any significant banding (pattern noise) or heat bloom.
Color balance was pretty neutral with Canon Rebel SL1's Auto white balance setting (just a touch cool), even at high ISOs, though white balance took on a slightly red or magenta tint at lower light levels.
The Canon SL1's Multi Shot Noise Reduction mode takes a burst of four images and blends them together to average out noise. It really makes a difference at higher ISOs, making very high ISOs like 12,800 and 25,600 much more usable. As expected, it makes little difference at low to moderate ISOs, where noise is already low. Compare rows in the table above.
When using the optical viewfinder and phase-detect AF, the Canon Rebel SL1's autofocus system was able to focus on the subject down to just below the 1/8 foot-candle light level unassisted with our Sigma f/2.8 lens, and in complete darkness with AF assist enabled. In Live View mode using Hybrid AF, the Canon SL1 was able to focus down to just above the 1/2 foot-candle light level, which is poor for a DSLR with an f/2.8 lens.
As always, keep in mind that the longer shutter speeds here demand the use of a tripod to prevent any blurring from camera movement. (A useful trick is to just prop the camera on a convenient surface, and use its self-timer to release the shutter. This avoids any jiggling from your finger pressing the shutter button, and can work quite well when you don't have a tripod handy.)
How bright is this? The one foot-candle light level that this test begins at roughly corresponds to the brightness of typical city street-lighting at night. Cameras performing well at that level should be able to snap good-looking photos of street-lit scenes.
NOTE: This low light test is conducted with a stationary subject, and the camera mounted on a sturdy tripod. Most digital cameras will fail miserably when faced with a moving subject in dim lighting. (For example, a child's ballet recital or a holiday pageant in a gymnasium.) Digital SLRs like the Canon SL1 do much better than point & shoots, but you still shouldn't expect a quick autofocus lock with moving subjects.
Good 24 x 36 inch prints at ISO 100/200; makes a good 16 x 20 inch print at ISO 800 and a usable 4 x 6 at ISO 12,800.
ISO 100/200 can produce great 24 x 36 prints if you look at them from a typical viewing distance, while a 20 x 30 inch print looks wonderful. You are pushing the resolution of the 18-megapixel sensor once you go past 20 x 30 inches, as you can see tiny pixilation on the edges if you look very closely. However, image quality is still impressive with excellent fine details and bright, accurate colors. ISO 100 and 200 prints are nearly identical, with maybe just a tiny fraction more detail in ISO 100, but it's extremely hard to tell the difference. Despite the 18-megapixel resolution, 30 x 40 inch prints would do fine for wall display.
ISO 400 allows for great prints up to 20 x 30 inches, while 24 x 36 inch prints are suitable for wall display.
ISO 800 images look good at 16 x 20 inches. There is a hint of noise, but you only really notice it in the shadow areas. 20 x 30 inch prints are suitable for wall display.
ISO 1600 makes a good 13 x 19 inch print with a nice level of fine detail. Colors also looked accurate and pleasing. At 16 x 20, the image is a bit too soft in finely detailed areas for us to make the call at that size. Noise starts to appear a bit in the shadows if you look closely, but noise in the highlights and midrange areas are very low.
ISO 3200 prints start to show a bit more noise in the shadows, and the SL1 starts to have noticeable issues with red colors (particularly in our red fabric area of our test scene), but it still produces a nice 8 x 10 inch print. As before, shadow noise is apparent, but otherwise the image looks great and fine details are still noticeable.
ISO 6400 makes a decent 5 x 7, but noise and a reduction in fine detail starts to degrade image quality, preventing us from calling anything larger acceptable.
ISO 12,800 images are fairly heavy on noise and lack fine detail at larger sizes, but can still produce a decent 4 x 6 inch print. Colors still look okay, if a little on the dull side.
ISO 25,600 images were too mushy on fine detail and high ISO noise was very apparent, and therefore we would recommend avoiding this ISO level for use in prints.
The Canon Rebel SL1 uses an 18-megapixel APS-C sensor that's very similar to the one housed inside the Canon T4i & T5i, and produces excellent results for large prints at low ISO levels, all the way up to wall-mountable 30 x 40 inch prints at ISO 100 and 200. Additionally, this camera did surprisingly well in handling noise and grain at higher ISO levels. It wasn't until you got to ISO 6400 and looked very closely at the shadow areas that you began to see noise as well as noticeable degradation in fine detail. Once you get up to ISO 12,800, things start to look a little bleak, although we still thought a 4 x 6 inch print looked acceptable. At ISO 25,600, the lack of fine detail and high ISO noise levels made it difficult for us to call any size acceptable. All in all, a solid performer from Canon with its micro-sized DSLR.
Testing hundreds of digital cameras, we've found that you can only tell just so much about a camera's image quality by viewing its images on-screen. Ultimately, there's no substitute for printing a lot of images and examining them closely. For this reason, we now routinely print sample images from the cameras we test on our Canon Pro9000 Mark II studio printer, and on the Canon Pixma MP610 here in the office. (See the Canon Pixma Pro9000 Mark II review for details on that model.)