Canon T4i Digital Camera Review$1,199.00
There are four noise reduction settings on the T4i: Low, Standard, High, and Multi Shot. You can also turn noise reduction completely off, though our testing showed that it is still applied to some degree even at base ISO. Multi Shot is a new noise reduction setting for the T4i; it takes four consecutive exposures and combines them to reduce noise. We found it to be the most effective of all, though it can be difficult to use handheld, particularly in the sorts of situations where you'd most want to use it (in low light, for instance).
Of the conventional noise reduction settings, Standard produced the best results. It avoided smearing detail below ISO 800, and then ramped up its efforts at the higher sensitivity settings. With Standard noise reduction enabled (or when shooting RAW and developing in Lightroom), images come out looking quite usable up to about ISO 6400. Even at higher noise reduction settings, ISO 12800 isn't great, and 25600 isn't really usable no matter what you do—it just creates a blotchy mess that we'd be embarrassed to show anyone.
As with the T3i, the new model produces more noise in the blue and red channels than in the yellow and green. This is good news for leaf peepers and bad news for people who like to shoot the sky (or Ferraris). More on how we test noise.
The native ISO range on the Canon T4i goes from 100-12800 by default, and can be expanded to encompass 25600. The camera's automatic ISO mode allows you to set a maximum limit of up to ISO 6400, but doesn't let you set the minimum ISO. Note that when using the Highlight Tone Priority option, the lowest and highest ISO settings are not available.
Like the T3i, the Canon T4i has nine autofocus points, but in this case all nine sensors are cross-type (the more accurate variety). It also boasts a new "hybrid" live view autofocus system, which uses phase-detect AF pixels on the imaging sensor itself to quickly determine subject distance, and then uses contrast-detect AF to add extra focus precision.
Autofocus is quite accurate and pretty quick in traditional TTL phase-detect mode; there's no real speed improvement over the T3i, but it does feel slightly more accurate. Live View is definitely quicker, and very accurate. It also over-shoots its target much less often in its attempts to achieve a focus lock.
Performance in low light is pretty good, though it still struggles and often simply fails to find focus in situations with very poor lighting and a low-contrast subject. Historically, this has been pretty standard behavior for DSLRs up till now, though with the advent of AF systems with -3 EV focus sensitivity (such as the Pentax K-5 II and the Canon EOS 6D) this could change. The T4i also lacks a focus assist beam, instead using a short pulse from its pop-up flash to illuminate a scene and grab focus. This is a little annoying in practice, and definitely an inferior solution in terms of actual effectiveness, so we're sad Canon couldn't pony up for a LED-based beam.
Video: Low Light Sensitivity
We tested the Canon T4i's low-light sensitivity under lab conditions and found that it needed only 5 lux of light to produce an image that achieved 50 IRE on a waveform monitor (i.e., a fairly acceptable image that, while dark, is still visible with some degree of detail). By way of contrast, the T3i required 8 lux to achieve the same feat. The T3i's mark was already a good one, and the T4i's is superb for a camera in its class.