Canon T6i Flash

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

Coverage. Canon rates the EOS T6i's internal flash coverage at approximately 17mm, though as you can see in the above shot taken at 18mm, we've found manufacturers' coverage ratings are usually quite optimistic. Peripheral Illumination Correction was on (by default) for this shots, so the fall-off seen here in the corners and vertical edges is mostly from the flash itself.

Exposure. Indoors, under incandescent background lighting, the Canon T6i's flash performed very well, requiring the typical +0.7 EV positive exposure compensation needed for this test scene at ISO 100 and f/4, with the camera selecting a shutter speed of 1/60s. (Note that we normally take this shot at ISO 200, but the T6i's flash was powerful enough to produce a bright image at ISO 100, so we didn't retake it.) The camera's slow-sync flash mode didn't require exposure compensation for a good exposure, though the longer exposure (1/20s) resulted in a warmer orange/yellow cast from the ambient background lighting.

Manufacturer Specified Flash Test. The Canon T6i's built in flash has a rated Guide Number of 12 meters or 39.4 feet at ISO 100. That works out to about 7.0 feet at f/5.6. In the shot above at those settings, we can see that the Canon T6i's built-in flash didn't quite perform to specification, producing a slightly dim flash target at the rated distance. The image was only underexposed by about 1/3 EV though.