Panasonic GX7 Flash

Coverage and Range
A small, weak flash with uneven coverage at wide angle. Above average positive exposure compensation required.

Coverage. Flash coverage is rather uneven at wide angle, leaving the corners of our flash target image darker at 14mm, thought that's not unusual. Some of the corner shading can also attributable to the lens itself. Coverage is more uniform at full telephoto (42mm), though our target is quite dim.

Exposure. Indoors under incandescent background lighting, the Panasonic GX7's flash underexposed our indoor portrait scene at ISO 200, despite the +1.0 EV flash exposure compensation used. (An average of +0.7 EV is normally needed for this shot.) You'll likely need to boost ISO (or enable Auto ISO) for typical indoor shots. The camera's slow-sync flash mode required no compensation to produce a bright shot, though the longer shutter time resulted in a much warmer cast from the ambient background lighting.

ISO 200 Range. At full wide angle, flash exposures are usable out to about 8 feet, with brightness decreasing gradually with distance from there. At full telephoto, flash exposures started out quite dim at 6 feet (as expected), and brightness fell off rapidly from there.

Manufacturer-Specified Flash Range Test. The Panasonic GX7's built-in flash has a Guide Number of 5m at ISO 100, or 7m at ISO 200. That works out to about 6.6 feet at f/3.5 and 4.1 feet at f/5.6, the maximum apertures the kit lens has at full wide angle and telephoto respectively. As you can see above, the Panasonic GX7 produced a good flash exposure at the rated distance at wide angle (the flash target is just slightly overexposed), but results at 42mm are quite dim. Given the results at wide angle are bright, we'd say that Panasonic's GN rating is credible. Our standard test method for flash range uses either 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 (at Auto ISO if so specified), to assess the validity of the specific claims.