Overall Performance

Overall, the Panasonic Lumix DMC-GX1 is an impressively nimble performer. Whether changing settings via the touchscreen, physical control points or a combination of the two, menus and settings are quite responsive. From power-on to first exposure using the camera's AF takes around 1.4 seconds, but once powered on, shutter press to image capture can happen in as little as 0.2 seconds including AF acquisition and within 0.1 seconds with the camera pre-focused. Even in raw-enabled continuous shooting modes, buffer overruns do not prevent you from taking additional images, albeit at a slower rate. We generally found the camera ready to shoot when we were.

The GX1's combination of a mode dial, four Fn buttons (two onscreen), numerous control points on the rear of the camera and a comprehensive touchscreen interface means that you can make between-shot adjustments quickly and easily, often with multiple options at your disposal for accessing the same setting. Few key camera settings involves an inordinate amount of clicks or presses. This contributes to an overall feeling of responsiveness when using the GX1.

Continuous Shooting and Buffering

Like the Panasonic Lumix DMC-G3, the GX1 has four burst modes, SH, H, M, and L. We'll discuss the SH mode in the following section, but in H mode, using the static AF setting, the GX1 shoots at up to 4 frames per second at its highest image quality settings. In M mode, image capture drops to 3 fps, which is still quite usable for shooting casual action. It bears mention, however, that live view is disabled in H mode, so the gain of one additional frame per second is tempered by the fact that you cannot see what the camera is actually capturing, only the image that it has just recorded. Although this generally isn't a problem when shooting static subjects, the lack of live view greatly reduces your ability for instance, to pan accurately while following a subject. In a noticeable improvement over the G3, the GX1's buffer can capture up to 28 JPEG images at its maximum frame rate. Crucially, images can still be shot while the camera is writing data to the card. It's hard to overestimate the importance of being able to shoot images - even at a reduced frame rate - while the buffer is being emptied. During this time of data transfer you can also access camera menus, with the exception of, understandably, the playback menu.

To generate the timings shown below, we shot with the camera's burst mode set to H, with a SanDisk Extreme Pro SDXC class 10 card.

Burst of JPEG 16MP/Fine images

64 GB SanDisk Extreme Pro
Frame rate 4 fps
Number of frames 28
Buffer full rate 2 fps
Write complete 5 sec.

Burst of RAW images

64 GB SanDisk Extreme Pro
Frame rate 4 fps
Number of frames 11
Buffer full rate 0.77 fps
Write complete 13 sec.

Burst of RAW plus JPEG 16MP/Fine images

64 GB SanDisk Extreme Pro
Frame rate 4 fps
Number of frames 8
Buffer full rate 0.5 fps
Write complete 18 sec.
The results shown above are impressive, placing the GX1 among the top performers of any Micro Four Thirds camera we've seen. While a top shooting speed of 4fps is not going to hold up for a dedicated sports photographer, the fact that in Raw+JPEG mode you can shoot up to 8 frames at this rate and then continue shooting single images without waiting for the buffer to empty is, we suspect, of great practical benefit for many users.

20fps Drive mode (4Mp)

The GX1's SH burst mode captures 4MP images at 20 frames per second. In the current G-series lineup the GX1 joins the Panasonic Lumix DMC-G3 and the Panasonic Lumix DMC-GH2 as cameras capable of double-digit frame rates. The image sequence you see below was shot with the G3.

This short sequence gives you some idea of what 20fps looks like when SH continuous shooting mode is engaged.

There's no such thing as a free lunch, however, and to achieve 20fps you have to accept some sacrifices. The first thing you give up is live view. Just like shooting in 'H' continuous mode, during a 20fps capture burst the viewfinder/LCD screen displays a review of the images already captured, as opposed to a real-time view of the scene.

In addition, the resulting images are 4MP JPEGs (Raw mode is disabled when SH is selected). At a resolution of 2272 x 1704 you have, in theory, enough pixels for a decent quality 8x10 print. But there is a steep penalty to be paid in terms of image quality. The 20fps files exhibit prominent artifacts and are noticeably short on fine detail.

Shooting in SH burst mode yields noticeably inferior image quality than that of a conventional 4MP capture. Above you see 100% crops of an SH burst mode image on the left, and on the right is the same scene captured by the GX1 when set to a 4MP single shot mode. The two files have the same pixel dimensions but you can easily see loss of detail and jagged edges in the frame captured in SH mode.

With such a drastic reduction in image quality, SH mode is best suited to images destined for the web or very small prints.

Autofocus speed / accuracy

We have always been impressed with the AF performance of the G-series cameras compared with competitive systems that also use contrast-detection AF and even some entry-level DSLRs. The GX1 continues this trend. Panasonic claims AF acquisition times for the GX1 that are 10% faster than the already speedy G3. To be honest, in practical use this difference is negligible. Yet with a sensor readout capable of sampling 120 times per second, the GX1's speedy focus acquisition will be a noticeable upgrade for users coming from the GF1. In well lit scenes of static subjects with strong contrast, using both the standard Lumix G Vario 14-42mm F3.5-5.6 ASPH OIS and power zoom Lumix G X Vario PZ 14-42mm kit lenses, we found acquisition times from shutter press to image capture as fast as 0.2 seconds which is very impressive indeed.

Of course, the Achilles heel of any contrast-detection AF system is low light, poor subject contrast or a combination of the two. Overall, we found performance with the kit lenses in these environments to be roughly on par with that of entry-level DSLR kit lens combinations.

Panasonic GX1 with Leica D Summilux,
ISO 12,800, 1/60 sec f/3.2
Even in this low light indoor scene, face detection (simulated by yellow brackets) was able to lock onto the subject, and then acquire focus almost immediately.

While such a high ISO has obvious image quality trade-offs, as you can see in this 100% crop, the ability of the GX1's AF system to successfully focus on a subject in such low light is impressive.

When using one of Panasonic's fast prime lenses, however, like the Leica D Summilux Asph 25mm F1.4 we were very impressed with the AF system's ability to quickly lock focus on static subjects indoors even under low light conditions. In the sample above, the camera was used in shutter priority, with a custom white balance and exposure compensation of +.33EV to provide a pleasing luminance level.

AFC tracking

When set to AFC mode (continuous autofocus) the GX1 employs its contrast-detection AF to track the subject. Based on the tracking performance of previous G-series models we were not expecting miracles here, and our experience of shooting has proven that our caution is justified. Results were on par with what we experienced with the Panasonic Lumix DMC-G3.

We found the GX1's AFC tracking to be most successful in well-lit scenes with subjects of strong contrast that move rather consistently. When panning the camera in order to keep the subject relatively close to the central area of the viewfinder/LCD screen, we were only able to reach success rates as high as 50% with very slow moving subjects. In and of itself, we feel that AFC tracking on the GX1 is a reasonable option as long as you set your expectations accordingly. Yet, with the introduction of the Nikon 1 V1 and its benchmark setting AF tracking capability, the GX1- like most other mirrorless and even entry-level DSLRs - is now looking up at a new standard of performance.