This tab lets you calculate the depth of the field of acceptable sharpness in a displayed image. This depends on the subject distance, focal length, aperture, and the circle of confusion (CoC). The program calculates the CoC value based on the film size, but you can put your own value in, if you like.
When you focus your camera’s lens at a certain subject distance, objects at exactly that distance from the camera are exactly in focus. Technically, everything else is out of focus. The transition from perfect focus to the smallest perceptible amount of softness is gradual, so there is a “field of acceptable sharpness” surrounding the focal plane. The size of this field is called the “depth of field.” Objects within this field of acceptable sharpness are considered in-focus, and those outside the zone are out-of-focus.
There are some general rules about depth of field:
Smaller apertures (larger ƒ numbers) make for deeper in-focus fields.
Wide angle lenses have deeper field depths at a given aperture than telephoto lenses do.
To calculate depth of field, ƒ/Calc first needs to find h with Equation 4.1, “hyperfocal distance”. It can then find the distance to the near and far edges of the field of acceptable sharpness from the focal length of the lens f and the subject distance s.