The ExpoAperture Depth-of-Field Guide, made by ExpoDisc, is a mechanical calculator made up of three circular plastic discs that rotate against one another, effectively functioning as a circular slide rule.
The discs – which are printed front and back â€“ instantly shows the relationship between focal length, focus distance, aperture and resulting depth-of-field.
Using the ExpoAperture DOF guide, a photographer simply dials in the camera’s sensor or film size and desired focal length for a given shot. The guide quickly provides the resulting depth-of-field for a given aperture, or, alternatively, determines the aperture necessary to achieve a desired depth-of-field.
It is intended for use as an educational tool for novices to understand and master the DOF concept, but is also useful for even experienced photographers so they can quickly compare the relative variables (aperture, lens focal length and subject distance) to determine which combination works best for their chosen shot.
The ExpoAperture DOF guide works with nearly any camera, digital or film, regardless of sensor size or film format.