Canon EOS T1i (Rebel T1i, Canon 500D)

Canon T1i Flash

The Rebel T1i's built-in flash has a guide number rating of 43 feet (13 meters) at ISO 100, translating to a range of about 15 feet at ISO 100 with an f/2.8 lens. The Canon Rebel T1i gives you a great deal 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 T1i also uses E-TTL II control for both the built-in and compatible external flashes (according to Canon this includes the older 550EX flash, as well as the newer models), a standard that promises, and seems to deliver, better, more balanced exposures. (TTL refers to "Through The Lens" metering.)

Another nice touch is the Canon T1i's Flash Exposure Lock button, 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 T1i's pentamirror housing, for use with external flash units. Like most consumer SLRs, the Canon T1i offers no PC-Sync connector for triggering studio strobes, etc.

Several of the more impressive features of the Canon flash system depend on the dedicated 430EX II, 580EX, and 580EX II Speedlites. Among these are 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. On the Canon Rebel T1i, this requires a flash duration of 1/200-second. Uniform, long-duration flash pulses like this permit use of shutter speeds as high as the 1/4,000-second maximum that the Canon Rebel T1i is capable of. This can be invaluable when you want to exclude ambient light from the exposure.

New Dedicated Flash Unit: Canon 270EX

The Canon T1i can also use the new too-cute-for-words 270EX flash unit that was announced at the same time as the new camera. Despite it's diminutive outline, the new 270EX packs a noticeably bigger punch than the Canon T1i's built-in strobe (wide-angle guide number of 72 vs 43 feet, 22 vs 13 meters), but it also can set itself for either wide-angle or telephoto coverage. In telephoto mode, it has a coverage angle roughly equal to that of a 50mm lens, and the concentration of its light output increases its guide number to a remarkable 89 feet / 27 meters. The new strobe also sports a rotating head, that can tilt up to angles of 60, 75, and 90 degrees, for bounce-flash operation. A pretty neat set of features and capabilities from such a compact and inexpensive dedicated strobe unit.

Flash Test Results

Coverage and Range
Good flash performance, but rather uneven coverage at wide angle. About average positive exposure compensation required.

Wide Angle	Telephoto
Normal Flash +0.7 EV	Slow-Sync Flash +0.3 EV

Coverage and Exposure. Flash coverage was very uneven at wide angle with the Canon T1i, with falloff in the corners of the frame extending deep into the frame. Coverage at telephoto is more even. Indoors, under incandescent background lighting, the Canon T1i's flash performed quite well, requiring about average positive exposure compensation of +0.7 EV for a reasonably bright image. With the camera's slow-sync flash mode only required a +0.3 EV boost, though the longer shutter time results in a warmer cast from the ambient background lighting.

Flash Range: Wide Angle
6 ft	7 ft	8 ft	9 ft	10 ft	11 ft
1/64 sec f3.5 ISO 100	1/64 sec f3.5 ISO 100	1/64 sec f3.5 ISO 100	1/64 sec f3.5 ISO 100	1/64 sec f3.5 ISO 100	1/64 sec f3.5 ISO 100
12 ft	13 ft	14 ft	15 ft	16 ft
1/64 sec f3.5 ISO 100	1/64 sec f3.5 ISO 100	1/64 sec f3.5 ISO 100	1/64 sec f3.5 ISO 100	1/64 sec f3.5 ISO 100

Flash Range: Telephoto
6 ft	7 ft	8 ft	9 ft	10 ft	11 ft
1/64 sec f5.7 ISO 100	1/64 sec f5.7 ISO 100	1/64 sec f5.7 ISO 100	1/64 sec f5.7 ISO 100	1/64 sec f5.7 ISO 100	1/64 sec f5.7 ISO 100
12 ft	13 ft	14 ft	15 ft	16 ft
1/64 sec f5.7 ISO 100	1/64 sec f5.7 ISO 100	1/64 sec f5.7 ISO 100	1/64 sec f5.7 ISO 100	1/64 sec f5.7 ISO 100

ISO 100 Range. The Canon T1i's flash was bright and powerful. Set to its maximum 18mm wide angle setting, the test shots showed no falloff in brightness all the way to the 16-foot limit of our test. At full telephoto, flash intensity started out a little dim, but maintained good brightness until about 10 feet at 55mm.

Manufacturer-Specified Flash Range
Wide Angle	Telephoto
12.0 feet ISO 100	7.5 feet ISO 100

Manufacturer Specified Flash Test. The Canon T1i's built in flash has a rated Guide Number of 13 meters at ISO 100. That works out to 12 feet at f/3.5 and 7.5 feet at f/5.6. In the two shots above, we can see that the Canon T1i's flash performs to specification, producing bright images at both zoom settings.

Note: Our standard test method for flash range uses a fixed setting of ISO 100, 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.