Kelly Calculator

A Kelly Calculator is used to determine the depth of field for a given lens focal length and f stop.

The Kelly Calculator is a small flat disc which easily fits into any camera bag or focus puller's pocket and makes ascertaining what is and isn't in focus very straight forward. Very handy if an actor has slightly missed the mark or the focus is slightly off the ideal point, the Kelly can be used to decide whether or not to do another take for focus reasons.