These lenses place the rear of the lens closer to the camera's sensor (referred to as short back focus).

On the back of these models there is a hole covered by a black plug, presumably for back focus calibration.

However, not all such lenses require the shorter back focus, and may feature the standard EF mount.

The camcorder's only responsibility at this point is to record what is being projected onto the focusing screen (called back focus.)

With some individual lenses not quite calibrated it may consistently front or back focus, and may consistently focus in the wrong spot.

Furthermore, as the autofocus system does not calculate whether the subject is in front focus or back focus, focus tracking is not feasible.

Therefore, CDAF systems are not prone to calibration issues such as front or back focus as can occur with phase detect systems.

A vast majority of Ontario Reform supporters backed Focus Federally, and Grassroots United lost their bid to have the party enter Ontario politics.

BACK FOCUS as Eric lifts off his neck Shelly's ring for Elly's inspection.

In the field of video production, where it is often called a "back focus chart", the Siemens star is widely used to adjust the back focus of removable lenses.

The wide opening allows the lens to be mounted deeper within the body - up to 7.5mm (approx) from the mount surface - reducing the back focus distance of each lens to the minimum possible.

The two images are then analysed for similar light intensity patterns (peaks and valleys) and the separation error is calculated in order to find if the object is in front focus or back focus position.

The back focus of the body was the thinnest of any 35 mm camera, and as a result, it was possible to make adapters to use lenses designed for almost any other 35 mm SLR on an Alpa.

Forward or back focus does not occur with contrast focus like it can when using DSLR phase focus, and likewise each lens does not have to be individually calibrated to each camera, which can be required for DSLRs to have accurate focus.