Canon T4i Exposure

Saturation & Hue Accuracy
Very good saturation and excellent hue accuracy.

Saturation. The Canon EOS Rebel T4i produces images with fairly accurate saturation levels. Strong reds, oranges, dark greens and dark blues are pushed a little, while yellow and cyan are slightly muted. The mean saturation of 108.3% (8.3% oversaturated) at base ISO is not too pumped yet not too dull, and saturation remains fairly consistent over the ISO range except at ISO 25,600 where it drops off noticeable. Most consumer digital cameras produce color that's more highly saturated (more intense) than found in the original subjects. This is simply because most people like their color a bit brighter than life.

Skin tones. The Canon T4i 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 T4i'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 3.23, which is outstanding, one of the best scores we've recorded to date. Hue is "what color" the color is.

Saturation Adjustment
The Canon EOS Rebel T4i 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 T4i'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.

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.

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.

Indoors, under incandescent lighting, the Canon EOS Rebel T4i'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 T4i 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 T4i 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.)

Outdoors, daylight
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.

Outdoors, the Canon EOS Rebel T4i tended toward a slightly cool color balance, though overall color was generally very good. The Canon Rebel T4i 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 T4i'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.

See full set of test images with explanations
See thumbnails of all test and gallery images

Resolution
Very high resolution, 2,000 ~ 2,100 lines of strong detail.

Our laboratory resolution chart showed the Canon Rebel T4i's images with sharp, distinct line patterns down to about 2,000 lines per picture height horizontally and about the same vertically. 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 slightly more resolution than the in-camera JPEG, perhaps 100 lines, though complete extinction of the pattern was extended well past 3,200 lines in both directions in the converted files. While ACR was able to extract more detail, it also produced more color moire 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.

See full set of test images with explanations
See thumbnails of all test and gallery images

Sharpness & Detail
Good sharpness and loads of detail with a sharp lens. Some minor detail loss to noise reduction processing even at low ISOs.

Sharpness. The Canon EOS Rebel T4i'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 crop of our Far-field House 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 crop above of the hair 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 T4i does an excellent job of capturing sharp, detailed JPEGs when coupled with a sharp lens, but as is usually the case, slightly more detail can be preserved 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), 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 more fine detail than the DPP conversions, but also show more noise at default settings, which is not unusual. You may want to experiment with ACR's noise reduction settings to find the detail vs noise trade-off you're looking for. Regardless, the Canon T4i 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.

The Canon EOS Rebel T4i's high ISO performance is pretty good, very similar to the Canon T3i'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. At 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 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 strange diagonal bands in the strands of hair on the model'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 good performance, perhaps just slightly better detail retention compared to the T3i at higher ISOs. Noise is however generally a little higher than competing models. 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. Very good low-light performance.

The Canon EOS Rebel T4i 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 only average 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 T4i 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.)

Contrast Adjustment
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 T4i's contrast setting meets both challenges very well.

At its lowest contrast setting, the Canon T4i 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, especially when the contrast setting is tweaked.

The Canon Rebel T4i'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 T4i'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 the 60D, T2i and T3i, the Canon Rebel T4i 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.

Face Detection
Just like most point & shoot cameras these days, the Canon EOS Rebel T4i has the ability to detect faces in Live View mode, and adjust exposure and focus accordingly.

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 than the left image where face detection was not employed. Full Auto mode (right) however wasn't much better than Aperture Priority, despite selecting a larger aperture than we normally use for this shot (f/4.5 vs f/8).

Dynamic Range
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 T4i JPEG file with a nominally-exposed density step target (Stouffer 4110). At default camera settings and base ISO, the graph shows 11.1 f-stops of total dynamic range, with 7.41 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 T3i which uses a similar sensor with an older processor, the T4i scored slightly higher at the High Quality level (7.41 vs 7.31 f-stops), and significantly higher in total dynamic range (11.1 vs 9.95 f-stops). 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. The Canon T4i's raw file scored 0.8 f-stop more in total dynamic range (11.9 vs 11.1 f-stops) but the score at the highest quality level increased only 0.15 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 T3i at the High Quality level (7.56 vs 7.63 f-stops), though the total dynamic range score was higher like the JPEG, at 11.9 vs 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 EOS Rebel T4i 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).

Color balance was pretty neutral with Canon Rebel T4i's Auto white balance setting (just a touch cool), even at high ISOs, though at lower light levels white balance took on a slightly red or magenta tint. We didn't spot any issues with hot pixels, and only some very faint horizontal banding can be seen in darker areas at very high ISOs, but that's not unusual and shouldn't be a problem for properly exposed subjects.

The Canon T4i's new 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 T4i'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 T4i was able to focus down to just below the 1/2 foot-candle light level, which is poor for an SLR 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 T4i do much better than point & shoots, but you still shouldn't expect a quick autofocus lock with moving subjects.

Print Quality
Good 24 x 36 inch prints at ISOs 100/200; ISO 3,200 shots are better at 8 x 10; and ISO 12,800 makes a good 4 x 6.

ISO 100 shots are very nice at 24 x 36 inches, with sharp detail across the board except for our hard to please (er, render) red fabric swatch.

ISO 200 images also look quite good at 24 x 36.

ISO 400 prints nicely at 20 x 30 inches.

ISO 800 shots are slightly soft at 16 x 20 inches, with minor noise in a few shadowy areas, but are still quite good.

ISO 1,600 prints are quite good at 13 x 19. At 16 x 20, noise suppression has started to affect reds, and some luminance noise affects the shadows.

ISO 3,200 shots are better printed at 8 x 10.

ISO 6,400 images are a bit rough at 8 x 10, but are reasonably nice at 5 x 7.

ISO 12,800 images are decent at 4 x 6, although with a slight loss in color fidelity.

ISO 25,600 prints are not usable.

Overall, a pretty impressive performance from the Canon T4i, especially up to ISO 1600.

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.)