Panasonic GX8 Performance

Generally very good performance for a mirrorless ILC.

Startup time was a little faster-than-average for a mirrorless camera, and switching from Play to Record and taking a shot was fairly quick.

The Panasonic GX8's autofocus speed was very good our tests, especially for a camera that uses contrast detection only. The GX8 produced full-autofocus shutter lag (with the subject at a fixed distance) of 0.177 second using 1-area (center) AF. That's quite good for a mirrorless camera and competitive with most prosumer DSLRs. When manually focused, the GX8's lag time dropped to 0.065 second, also very good. The GX8's prefocused shutter lag time was 0.058 second, also quite fast.

To minimize the effect of different lens' focusing speed, we test AF-active shutter lag with the lens already set to the correct focal distance.

Single-shot cycle times were so fast that they were difficult to accurately measure as they depend on the tester's dexterity and ability to maintain an optimum rhythm, so your results may vary. (Note that we no longer test single-shot mode with just RAW files, as the results are usually somewhere in between JPEG and RAW+JPEG.)

Continuous High Speed "H" mode burst rate was quite good for its class at 8.3 frames per second for best quality JPEGs, slightly exceeding Panasonic's 8 fps spec. When shooting RAW or RAW+JPEG files, the frame rate dropped only slightly to 7.9 fps, which is still quite good. Note that these burst rates are with single-shot AF mode (AFS). Panasonic claims up to 6 fps with continuous autofocus (AFC). The GX8 also offers Middle Speed (rated at about 6 fps) and Low Speed (rated at 2 fps) modes, however we did not test those modes.

The GX8 has an all-electronic shutter mode which the company says boosts the full-resolution frame rate to 10 fps with AFS, but when we tested it in the lab, it was actually slower than with the mechanical shutter (~7.2 fps for RAW+JPEG mode), so we didn't test with it further. A Super High Speed mode which uses the all-electronic shutter is also available which captures Small JPEGs (5 megapixels at 4:3) at 40 frames per second for up to 120 frames, however we did not test that mode in the lab.

Full-resolution buffer depth was essentially limited only by card capacity when shooting Large/Fine JPEGs. When shooting RAW files buffer depth was 36 frames, and 32 frames when shooting RAW+JPEG files, which is quite generous.

Buffer clearing was pretty slow with a fast 95MB/s UHS-I card, ranging from 20 seconds after a long burst of JPEGs to 39 seconds after a 32-frame burst of RAW+JPEG files. You can however take additional photos and adjust settings while the buffer is clearing. Oddly, there's no mention of UHS-II support for the GX8, but we tried a UHS-II card anyway. Unfortunately it didn't improve buffer depths or clearing times, confirming the UHS-II interface is not supported.

Bottom line, the Panasonic GX8's performance is very good for its class. Startup and mode switching are reasonably fast, while autofocus speed and shutter lag are very good. Burst performance is very good, buffer depths are excellent, however buffer clearing is slow.

Below average battery life.

The Panasonic GX8 uses a custom rechargeable lithium-ion battery pack for power, and comes with both a single battery and dedicated battery charger. The CIPA-rated 330 shots per charge when using the monitor and 310 shots with the EVF are below average for a mirrorless ILC (especially for one with no built-in flash), and much lower than a typical DSLR when using an optical viewfinder. We strongly recommend getting a second battery for your GX8 if you plan any extended outings.

The table above shows the number of shots the camera is capable of (on a fully-charged rechargeable battery), based on CIPA battery-life and/or manufacturer standard test conditions.

(Interested readers can find an English translation of the CIPA DC-002 standards document here. (180K PDF document))