Canon 70D Flash

Coverage and Range
Good flash range, though with somewhat narrow and uneven coverage. Average positive exposure compensation required.

Coverage. Canon rates the EOS 70D's internal flash coverage at approximately 17mm, though as you can see in the top left shot taken at 18mm, 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 in the corners and vertical edges is mostly from the flash. Coverage is also uneven vertically, with a dimmer horizontal band just above center. We doubt you'd notice this in most read-world flash shots, though. Coverage is more even at full telephoto, as expected.

Exposure. Indoors, under incandescent background lighting, the Canon 70D's flash performed well, requiring an average amount of positive exposure compensation of +0.7 EV for a bright image in our test scene with a shutter speed of 1/60s. The camera's slow-sync flash mode only required +0.3 EV exposure compensation for bright results, though the longer exposure (1/20s) resulted in a warmer orange/yellow cast from the ambient background lighting.

ISO 200 Range. At the kit lens' maximum wide-angle setting and aperture (18mm and f/3.5), our flash range test shots at ISO 200 started out a little dim at 6 feet, then got a bit dimmer before getting brighter, showing usable exposures out to about 12 feet. That's a little odd, because at the smaller aperture of f/5.6 at full telephoto, flash range was better with good exposures out to about 14 feet, though flash output again fluctuated somewhat with distance. It's possible that the multi-segment metering used may have been influenced by our white ceilings and doors at wide angle.

Manufacturer Specified Flash Test. The Canon 70D's built in flash has a rated Guide Number of 12 meters or 39.4 feet at ISO 100. That works out to about 11.2 feet at f/3.5 and 7.0 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 70D's flash did not quite perform to specification, producing slightly dim targets at the rated distances. It's not too far off the mark, though. At wide angle, exposure is about 1/4 EV underexposed, and at telephoto it's about 1/3 EV underexposed.

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.