Depth of Field Calculator
Near limit, far limit, total depth of field, and the hyperfocal distance for 35mm, medium format, and large format.
Depth of field is the band of distance, in front of and behind your point of focus, that still looks sharp in the final image. It depends on four things: focal length, aperture, how far away the subject is, and how big a blur spot the format can hide. That last one is the circle of confusion. A blur smaller than the circle of confusion reads as sharp; anything larger reads as soft. Bigger formats are enlarged less, so they tolerate a bigger circle, which is why each format here gets its own value.
The hyperfocal distance is the key number. It is the nearest distance you can focus on while still keeping infinity acceptably sharp. The formula is the focal length squared divided by the aperture times the circle of confusion, plus the focal length. Focus at the hyperfocal distance and everything from half that distance out to the horizon falls within depth of field. This tool computes it for you, along with the exact near and far limits for whatever subject distance you set.
How to use it
Choose your film format first, since it sets the circle of confusion. Enter the lens focal length, the aperture you plan to shoot, and how far the subject is in metres. The three cards give you the nearest and farthest points that will be sharp and the total depth between them. If the far limit reads "infinity", your subject is at or beyond the hyperfocal distance, so everything behind it is sharp too. The line underneath always shows the hyperfocal distance for the current settings.
Frequently asked
What is the circle of confusion?
It is the largest blur spot that still looks sharp to the eye at a normal viewing size. Anything blurrier than the circle of confusion reads as out of focus. Larger formats tolerate a larger circle because the image is enlarged less, which is why the value changes with format.
What is the hyperfocal distance?
The closest focusing distance at which everything from half that distance out to infinity is acceptably sharp. Focus there and you get the deepest possible depth of field for that aperture and focal length. It is the single most useful number for landscape and street work.
Why does depth of field depend on format?
Because larger formats use longer lenses for the same angle of view and are enlarged less, both of which affect the blur the eye sees. This tool sets the circle of confusion to a standard value for each format so the numbers reflect that.
Zone Light Meter for Android carries the same depth of field and hyperfocal calculator, tied to your chosen format, so you can set focus and aperture with confidence on location.