We're going to discuss how this follow-focus system is different.
There is no gearbox and there are no ring gears. Instead, the focus wheel features a soft, high-tech O-Ring that presses up against a focusing ring of a lens, and thus pressed up adjusts focus when the focus wheel is turned. This efficient design means convenience in swapping lenses.
The iDC Photo Video SYSTEM ZERO Follow-Focus XL2 W/ Camera Plate For Canon T3i & 70-200mm is a set consisting of two focus wheels, a T3i-specific camera plate, and a seven-slot focusing plate. The camera plate attaches to the bottom of the T3i. The focusing plate attaches to the camera plate. And the focus wheels slide into two of the seven dovetail slots of the focusing plate. The second focus wheel is included to work specifically with the zoom ring of a Canon 70-200mm lens.
The O-Ring mentioned above is replaceable yet very tough. A thumbscrew on the focusing plate tightens to keep the O-Ring pressed up against a lens. When the thumbscrew is loosened, the focus wheel that the O-Ring is featured on can be moved aside, thus facilitating a lens swap.
Our set is compatible with a very long list of lenses (see specs) because the focusing plate by means of seven slots was designed to accommodate a variety of lens constructions. And for those lenses that fall in-between the dovetail slots, the focusing plate slides for quick micro-adjustments.
The included focus wheels can be used with all iDC camera plates and thereby with DSLRs other than the T3i. The T3i-specific camera plate can also serve useful in adding viewfinders to the T3i; it holds in place via two screws compatible SYSTEM ZERO viewfinders, such as the iDC-modified Hoodman HoodLoupe, and thus enables quick-release functionality.
Our SYSTEM ZERO set can be mounted onto any shoulder rig or quick-release plate that accepts 1/4"-20 or 3/8"-16 fasteners.