Canon T4i Flash
Canon EOS Rebel T4i Flash
The Rebel T4i's built-in flash has a guide number rating of 43 feet (13 meters) at ISO 100, translating to a range of about 12 feet at ISO 100 with either kit lens at wide-angle (at f/3.5) and about 7.5 feet at telephoto (at f/5.6). Coverage is specified at 17mm or 28mm equivalent. The Canon T4i gives you a lot of control over flash exposure, allowing you to adjust flash and ambient exposure independently of each other, in one-half or one-third EV increments. This makes it easy to balance flash and ambient lighting for more natural-looking pictures. The Rebel T4i also uses E-TTL II control for both the built-in and compatible external flashes, a standard that promises and seems to deliver better, more balanced exposures. (TTL refers to "Through The Lens" metering.) Both evaluatative and average E-TTL II metering modes are available, and the flash can be timed to fire immediately after the first curtain opens, or right before the second curtain closes, allowing for motion trails that lead or follow the subject position at the moment the flash fires.
Another nice touch is the Canon T4i's Flash Exposure Lock function, which fires the flash under manual control before the actual exposure, to determine the proper exposure setting. This struck us as very handy, akin to the more conventional autoexposure lock function for handling difficult ambient lighting conditions. A Flash Exposure Compensation feature controls the flash exposure +/- 2 stops in 1/2 or 1/3-stop increments.
As you'd expect, there is a dedicated flash hot-shoe on the Canon T4i's pentamirror housing, for use with external flash units. Like most consumer SLRs, the Canon T4i offers no PC-Sync connector for triggering studio strobes, etc. Maximum flash x-sync speed is 1/200-second.
The 7D, 60D and T3i were the first Canon SLRs to support wireless flash control using the built-in flash, and the Canon T4i follows suit. That is, the T4i's built-in flash can act as a controller or commander to one or more remote wireless flashes. You can have the built-in flash contribute to the exposure, or just command the remote flashes. Like that of the 60D, the Canon T4i's wireless flash capability supports four channels and defines two groups (the 7D defines three groups). Exposure compensation and flash ratio of 1:8 to 8:1 can be set on a per-group bases, allowing a lot of control over how multiples flashes contribute to the final exposure. Additionally, there's an Easy Wireless Flash mode, which simply fixes the flash strobes to all operate as one group with a 1:1 flash ratio.
Canon's Speedlite 270EX, 270EX II, 320EX, 430EX II, and 580EX II (as well as certain of its historic flash models) enable advanced features such as true FP (focal plane, referred to as HS) flash sync, flash exposure bracketing with external flash units, flash modeling, and E-TTL II exposure control. FP sync requires a flash unit to provide uniform light output for a relatively long period of time, long enough for the focal plane shutter curtain to fully traverse the sensor plane. Uniform, long-duration flash pulses like this permit use of shutter speeds as high as the 1/4,000-second maximum that the Canon T4i is capable of. This can be invaluable when you want to exclude ambient light from the exposure.
Flash Test Results
Coverage and Range
A fairly powerful built-in flash, with somewhat narrow coverage. Average positive exposure compensation required.
|18mm @ f/3.5
||135mm @ f/5.6|
Coverage. Canon rates the EOS Rebel T4i's internal flash coverage at approximately 17mm, though as you can see in the top left shot, we've found manufacturers' coverage ratings are usually quite optimistic. Peripheral Illumination Correction was on (by default) for these shots, so the fall-off seen here is mostly from the flash. Coverage is more even at full telephoto, but exposure is quite dim in the top right shot.
Exposure. Indoors, under incandescent background lighting, the Canon Rebel T4i's flash performed well, requiring an average amount of positive exposure compensation of +0.7 EV for a bright image. The camera's slow-sync flash mode only required +0.3 EV exposure compensation for bright results, though the longer shutter time results in a warmer orange/yellow cast from the ambient background lighting.
ISO 200 Range. At the 18-135mm lens' maximum wide-angle setting, the flash range test shots at ISO 200 show bright results out to about 11 feet, with exposure falling off from there. At full telephoto (135mm), flash intensity varied but remained bright to 15 feet, so the range at wide-angle was likely limited by metering the bright ceiling, door and walls, and not by available flash power.
|Manufacturer-Specified Flash Range|
Manufacturer Specified Flash Test. The Canon Rebel T4i's built in flash has a rated Guide Number of 13 meters or 43 feet at ISO 100. At ISO 200, that works out to about 17.4 feet at f/3.5 and 10.8 feet at f/5.6, the maximum apertures of the 18-135mm lens at full wide-angle and telephoto respectively. In the shots above, we can see that the Canon Rebel T4i's flash doesn't perform to specification at wide-angle, producing an underexposed target. At full telephoto however, results are quite bright, so we conclude Canon's flash rating is credible, with metering of bright surfaces in the scene being the culprit at wide-angle.
Note: Our standard test method for flash range uses a fixed setting of ISO 200, to provide a fair basis of comparison between cameras. We've now also begun shooting two shots using the manufacturer-specified camera settings, at the range the company claims for the camera, to assess the validity of the specific claims.