Follow Focus
 

In looking at a video clip showing the d-Focus device just now, it looks like the gear ratios are set up so that one turn of the FF device is roughly equivalent to one turn on the lens barrel.

I noticed on Philip Bloom's "Learn2 to shoot" DVD that his Zacuto FF is set up so that the lens barrel moves a fraction of the distance that the FF disc does. This makes more sense to me, the way it "widens" a very precise point on the lens barrel. (I realize that different diameter lenses will behave slightly differently.)

So... has anyone compared the different FF systems with gear ratios in mind? Any other thoughts with regards to precision, backlash, bearing design that I should also keep in mind when shopping around for one of these? (Hard to do without a "hands on" trial).

It depends on the lens more than the FF.

You tend to get what you pay for with follow focus devices.