Autofocus
Perhaps the biggest recent advance in the Panasonic G-series cameras has been the faster contrast AF system found in the GH2. The fast readout from the Live MOS sensor, combined with a powerful processing system, means the GH2 has the fastest contrast-detection system found in any camera, almost rivalling phase detection in many circumstances.
The autofocus system of the G3 is based on that of the GH2, and I found it to be fast and snappy whether I was taking landscape or candid images. Having the ability to use the touchscreen to focus and then fire is wonderful. Furthermore, this feature has been improved in the G3 and now the entire touchscreen can be used to select the AF point.
In previous G-series cameras the edges of the frame could not be selected. With these improvements in mind I was keen to see exactly how far contrast-detection AF had advanced. In the past, the limitations of contrast-detection AF have meant that it is difficult to use when photographing subjects such as sports and wildlife, with the AF not being able to keep up with moving subjects.
For wildlife images my chosen lens was the Panasonic 100-300mm f/4-5.6mm optic. This gives the same field of view as a 200-600mm focal length on a 35mm camera. Although generally good, I found that the focal length was a little short for photographing wildfowl and rabbits in a field. If Panasonic were to make a 1.4x teleconverter, the focal-length reach of the 100-300mm lens would be ideal, although this may affect the focus speed.
As for the AF, it was good for photographing perched birds or grazing rabbits while in single AF mode. Continuous AF worked well for slight movements, but for faster moving subjects, such as birds in flight, the continuous AF struggles to keep up, although the 4fps shooting rate allowed me to capture one or two action shots. This was more down to timing and some careful pre-focusing, however. Similarly, focus tracking is useful for tracking birds walking, but it falls short as soon as movement becomes faster. Obviously, birds in flight and bounding rabbits are a real test for any camera in this price range, regardless of whether it uses phase- or contrast-detection AF. It is certainly possible to take wildlife images with the Panasonic Lumix DMC-G3, but you need a lot of practice and very careful timing.
Overall, the AF system of the G3 is significantly faster than that of the G2, and on par with the GH2, although it still lacks the speed to make it successful for action photography. For all other types of photography, the various focusing options of the G3 are excellent, and at times the contrast-detection autofocus is fast enough to fool you into thinking you are using a camera with phase-detection focus.
Of particular interest to landscape, macro and still-life photographers will be the new Pinpoint AF feature (see Features in use).
