Depth Of Field
Calculator

Depth of field depends on aperture, focal length, focus distance, and sensor size, with a wider aperture (smaller f-number), longer focal length, closer focus distance, and larger sensor all independently narrowing the zone of acceptable sharpness. The calculator combines all four into the standard depth-of-field formula based on the circle of confusion.

A wider aperture (smaller f-number) lets in a broader cone of light rays from off-focus points, which spreads out into a larger, more visibly blurred circle of confusion on the sensor, while a narrow aperture (larger f-number) restricts that cone, keeping more of the scene acceptably sharp. This is the core mechanism behind the classic 'blurry background' portrait look at f/1.8 versus deep-focus landscape shots at f/11 or f/16.

The circle of confusion is the largest blur spot that still appears as a sharp point to the human eye at normal viewing distance, and it depends on sensor size and expected print/display size. A larger sensor (like full-frame) tolerates a larger circle of confusion in absolute terms, which is part of why sensor size affects depth of field independent of aperture.

Depth of field is not symmetrical around the focus point, roughly one-third extends in front and two-thirds extends behind, because the near and far limits are governed by different relationships to focus distance in the underlying optics formula. This asymmetry becomes more pronounced the closer you focus.

No, depth of field is fixed at the moment of capture by the aperture, focal length, distance, and sensor size used, so cropping afterward doesn't change what was physically in focus, though viewing a cropped image at a larger relative magnification can make existing blur more visually apparent.