Canon 7D Flash
Canon 7D Flash
The Canon 7D's built-in flash has a guide number rating of 39 feet (12 meters) at ISO 100, translating to a range of about 14 feet at ISO 100 with an f/2.8 lens. That's not quite as powerful as the Canon 50D's flash, which was rated at 13 meters, but it's still a pretty healthy range. The Canon 7D 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 Canon 7D 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 7D'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 +/- 3 stops in 1/2 or 1/3-stop increments, a full stop more in both directions than the 50D's range.
As you'd expect, there is a dedicated flash hot-shoe on the Canon 7D's pentaprism housing, for use with external flash units. The Canon 7D also offers a PC-Sync connector for triggering studio strobes, etc. Maximum flash x-sync speed is 1/250-second.
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. Uniform, long-duration flash pulses like this permit use of shutter speeds as high as the 1/8,000-second maximum that the Canon 7D is capable of. This can be invaluable when you want to exclude ambient light from the exposure.
Flash Test Results
Coverage and Range
A moderately powerful flash with even coverage at wide-angle with the kit lens. Higher than average positive exposure compensation required.
|28mm @ f/3.5||135mm @ f/5.6|
Coverage. Flash coverage was fairly even at wide-angle with the Canon 28-135mm lens that will be bundled with the 7D as a kit in the US, but keep in mind that a 28mm lens has the field of view of about 45mm on the 7D, so the fall-off in the corners of the frame would likely be more noticeable with a wider-angle lens. (The 28mm example above was shot with the 7D's Lens Peripheral Illumination Correction enabled, so falloff due to the lens itself has been corrected.) Coverage at telephoto is also even, but quite dim in the test shot above.
Exposure. Indoors, under incandescent background lighting, the Canon 7D's flash required slightly higher than average positive exposure compensation of +1.0 EV for a reasonably bright image, and increasing to +1.3 EV actually reduced brightness. (The average is about +0.7 EV among the cameras we've tested.) With the camera's slow-sync flash mode only required a +0.7 EV boost, though the longer shutter time results in a warmer cast from the ambient background lighting.
ISO 100 Range. Since flash range depends on the aperture and therefore the lens used, we didn't take our ISO flash range series. We did however test at manufacturer specified ranges with the Canon EF 28-135mm f/3.5-5.6 IS lens below.
|Manufacturer-Specified Flash Range|
Manufacturer Specified Flash Test. The Canon 7D's built in flash has a rated Guide Number of 12 meters or 39 feet at ISO 100. That works out to 11.1 feet at f/3.5 and 7.0 feet at f/5.6. In the two shots above, we can see that the Canon 7D's flash performs almost to specification, producing usable but slightly dim 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.