- Location
- Seattle
- Name
- Andrew
Yeah, I looked into it a lot back when I got my GX85, the tech was touted as being especially good for tracking because it reduces the camera's need to rock back and forth to figure out which way to move the focus. In a modern lens with a fast AF motor (and a lens where only a single element is moved to attain focus) you mainly see the difference in continuous AF.
With a lens like the 20mm (which moves the whole/a lot of the lens elements to attain focus) the motor moves quite slowly in comparison. So for a fully 'dumb' contrast AF system (sorry, Olympus) the focus speed is glacial since it has to rock that slow focus motor back and forth, moving much greater mass inside the lens. DfD allows a Panny body to cut right to the correct focus by analyzing the out of focus characteristics and telling the lens which way it needs to move.
Incidentally, the Ricoh GR also moves the greater mass of its lens elements to attain focus, which is why it will never be a speed demon in focusing. But on the other hand, lens designs that work this way can be smaller and produce better image quality since they don't need additional room for focusing elements, which can cut down on sharpness. Essentially, the slowness of the 20mm is part of the reason why it's so sharp.
With a lens like the 20mm (which moves the whole/a lot of the lens elements to attain focus) the motor moves quite slowly in comparison. So for a fully 'dumb' contrast AF system (sorry, Olympus) the focus speed is glacial since it has to rock that slow focus motor back and forth, moving much greater mass inside the lens. DfD allows a Panny body to cut right to the correct focus by analyzing the out of focus characteristics and telling the lens which way it needs to move.
Incidentally, the Ricoh GR also moves the greater mass of its lens elements to attain focus, which is why it will never be a speed demon in focusing. But on the other hand, lens designs that work this way can be smaller and produce better image quality since they don't need additional room for focusing elements, which can cut down on sharpness. Essentially, the slowness of the 20mm is part of the reason why it's so sharp.