Camera Test: Canon EOS Rebel T4i

Nearly every year, we have a cover declaring the best Rebel ever. Even though we didn't do that this year, it would’ve been true if we had; Canon always manages to make improvements in its Rebel line.

With the EOS Rebel T4i ($849, body only), improvements include a new hybrid autofocus system that embeds phase-detection points on the CMOS imaging sensor, much like Nikon’s System 1 cameras. The new AF system works only with Canon’s new STM lenses that use stepping motors to move the elements inside the lens to achieve focus. When using such a lens, you gain reasonably fast continuous autofocus during live view or video shooting. While this system can’t match the speed of continuous focusing you can get with Sony’s transmissive mirror system found in that company’s DSLRs, it is a very big step in the right direction for Canon. At the same time, Canon also managed to improve the T4i’s noise handling over its predecessor.

In the Test Lab
Though the EOS Rebel T4i’s overall Image Quality rating of Excellent from ISO 100 through ISO 400 matches that of the T3i, don’t let that fool you. The T4i managed to keep noise at a Low or better rating a full two stops higher on the sensitivity scale than its predecessor. With nearly identical results in color accuracy and resolution, that's a pretty impressive achievement.

In our resolution test, the T4i served up 2560 lines per picture height, just enough to solidly earn it an Excellent rating. By ISO 800 this had fallen below the 2500 line cutoff for an Excellent rating.

Noise suppression is probably the T4i’s biggest strength in terms of imaging performance. Noise remains at a Low or better rating from the lowest sensitivty setting of ISO 100 through the camera’s sensitivity halfway point of ISO 1600. It doesn’t reach an Unacceptable noise rating until its highest sensitivity of ISO 25,600.

Since Canon applies increasing amounts of noise reduction as the ISO increases, there’s not much more room to bring noise down further at ISO 25,600. Depending on the image content, it might not be possible to bring it down to a noise level we’d rate as acceptable, but given our strict standards, some people may find some images shot with the T4i at ISO 25,600 usable, especially at magnifactions lower than 100 percent.

In our color accuracy test, the T4i walked away with an Excellent rating thanks to an average Delta E of 6.5. That’s well below our cutoff of 8 for this lower-is-better test.

Our autofocus test showed that the T4i’s regular phase-detection AF functions on par with what one can expect from an entry level DSLR. In very bright light it proved fast, focusing in 0.33 second in the brightest (12 EV) portion of our test. That’s not the fastest DSLR we’ve seen, but it’s still impressive. More impressive was that the T4i could focus in about 1.28 seconds at the dimmest light level (–2 EV) in our test. Some low-cost DSLRs won't even focus in such dim light.

The new hybrid AF system works in tandem with the standard phase-detection AF. When the mirror is flipped up for live view or video capture, the camera switches to the hybrid system. That uses both contrast detection and the special phase-detection points embedded in the CMOS sensor. These latter points let the camera see the distance to the subject in a way that the contrast-detection system can’t. The phase-detection points let the camera get very close to perfect focus, then the contrast detection brings it the rest of the way. In our experience with the new 40mm STM lens, the hybrid system provided much faster focusing than Canon’s previous attempts at contrast detection in DSLRs. But it wasn’t quick enough to keep up with faster-moving subjects during video or still capture. The standard phase-detection system had no trouble keeping up with triatholon runners and other faster-moving subjects.{C}{C}