Like other Panasonic cameras, the Panasonic GH5 uses a contrast detection autofocus (AF) system. This draws upon the imaging sensor for the information it needs to focus the lens and it looks at the brightness differences between pixels. When the AF system is active it aims to achieve the maximum brightness difference (or highest contrast) possible at a pixel level at the selected focus point.
The problem with a regular contrast detection system, and unlike a phase detection focusing system, is that it has no idea which way the focus needs to be adjusted to get the subject sharp. This means that it has to hunt, adjusting the focus backwards and forwards to assess the impact on contrast at a pixel level. It also doesn’t know when to stop which means the focusing overshoots, going beyond the point of focus so it has to adjust back again. These tiny adjustments can go unnoticed in good light, but it slows focusing. In low light levels the backwards and forwards adjustment is often more visible.
Panasonic introduced its DFD (Depth From Defocus) technology with the GH4 in February 2014 to help speed contrast detection focusing. It works by examining two images taken with the focus at different distances and analysing their sharpness so that the camera can determine which way and how far to adjust the lens to get the subject sharp. It all happens very quickly so you’re not aware of anything going on.
In order for DFD technology to work the camera needs to know the level of micro contrast that a lens can achieve and understand its bokeh, the quality of the out of focus areas. For this reason DFD focusing is only compatible with Panasonic’s lenses.
Although Panasonic’s DFD-enabled cameras have a database of information about the lenses that were current at the time of the body’s production, new lenses have the data stored inside them so that they can be used with existing DFD-capable camera bodies.
Panasonic GH5 DFD Focusing
The GH5 uses Panasonic’s most refined Depth from Defocus autofocus system to date. It performs more analysis of the scene to make the focusing faster and more decisive. It’s also better able to understand movement so it copes better with moving subjects than previous Panasonic cameras.
In addition, the GH5’s AF system benefits from the 480fps (frames per second) readout speed of the imaging sensor, giving a claimed FA response time of 0.05 seconds and the ability to use DFD focusing when shooting at 9fps in continuous AF mode or 12fps in single AF mode.