Performance

The Panasonic GM1 is an overall quick camera. It starts up and presents a focus target in about second, though it will take another moment to unlock the kit lens if needed. Auto focus with the kit lens is very good - at wide angle in good-to-moderate light it acquires focus in just a fraction of a second. At telephoto, jumping from very close to very far subjects in the same lighting conditions can take just a hair longer, but it's barely noticeable.

In the very darkest conditions the AF assist lamp comes to the GM1's aid. Focus slows down noticeably, as expected, stretching up toward a second at wide and telephoto. The screen also shows some noticeable lag, but is otherwise fluid in good lighting conditions.

Good light performance with the 20mm F1.7 was much the same as with the kit lens, but in dim light it's slightly slower. The GM1 is less likely to engage the AF assist lamp with the 20mm lens attached, and only relies on it in the very darkest of conditions. It will be unlikely to keep up with moving subjects in very dim light, but had no problem accurately focusing on static subjects, only occasionally hunting back and forth before finding its target. It also feels like the GM1 is doing quite a bit more work to move the elements of the larger lens, the likely reason why battery performance is worse with the 20mm as compared to the kit lens.

With a SanDisk Extreme Pro UHS-I card the GM1 permits reasonably fast shot-to-shot times shooting Raw+ Fine JPEG. With continuous full press and release of the shutter button it continued to shoot with slight hesitation about 1 frame per second, slowing down slightly around 5 frames and stopping briefly to clear the buffer around 8 frames. In Raw only it will continue up to around 20 frames on average before it hesitates, and shooting only JPEGs it will continue well beyond that to at least 50 frames (likely to card capacity).

Continuous Shooting and Buffering

The GM1 offers four continuous shooting modes: super high, high, medium, and low. The last two support live view during shooting, while the first two do not. The super high mode uses the electronic shutter, which allows the camera to shoot at a very fast top speed of 40 fps, albeit at a reduced 2272x1704 resolution. Here are the GM1's claimed burst rates per shutter mode:

 
Electronic Shutter
Mechanical Shutter
Super High
40.0 fps ---
High
10.0 fps 5.0 fps (with AFS), 4.0 fps (with AF-C)
Medium
4.0 fps 4.0 fps (with Live View)
Low
2.0 fps 2.0 (with Live View)

Panasonic claims the GM1 will record 7 images in each burst mode when there are Raw images being saved, and an unlimited number of frames recorded in JPEG-only, limited by card capacity. We found with a UHS-I card that it would just fall short of 7 frames in Raw or Raw+ mode at Medium burst rate before pausing to clear the buffer, but would continue shooting after a short pause. In our testing, the GM1 met or exceeded Panasonic's claims for burst speed.

 
Raw+ Fine JPEG
Raw
JPEG
Super High
--- --- 40 fps (39 frames)
High
5 fps (7 frames) 5.0 fps (7 frames) 5.3 fps (to card capacity)
Medium
5.0 fps (5 frames) 4.7 fps (6 frames) 4.7 fps (to card capacity)
Low
2.4 fps (7 frames) 2.2 fps (15 frames) 2.3 fps (to card capacity)

Battery Life

The GM1 ships with a rechargeable lithium-ion battery with a CIPA-rated 230 shots with the 12-32mm kit lens or 220 shots with the 20mm F1.7. That's well below the rest of the class, with most of its peers rating at least 350 shots. For all day shooting trips, an extra battery is a must.