Sidekick Lab Tools
Depth of Field Calculator
Conventional depth-of-field calculations usually assume a circle of confusion of 0.03 mm (30 µm) for 35 mm full frame. But that 0.03 mm is not a fixed, universal answer.
Blur grows continuously as you move away from the focus distance in either direction, and depth of field is calculated by deciding how much of that blur you accept. So even with the same lens, f-number and focus distance, changing the acceptable-blur criterion changes the depth of field.
In Sidekick Lab's depth of field calculator you can choose criteria other than the traditional 30 µm and see how the depth of field changes with the criterion.
Result
At close range, the difference between an actual lens and this model can become larger.
See how blur changes
Blur is smallest at the focus position and increases the farther you move in front of or behind it. The range below the green criterion line is the "depth of field" for this setting.
About this calculation
This calculation is a geometric depth of field based on an ideal thin-lens model.
The focus distance you enter is treated as the usual shooting distance from the sensor plane to the subject, approximating the difference from the front principal plane that the model needs as zero. This difference can become larger at close range.
With an actual lens, results may differ due to principal-plane position, internal focusing, aberrations, diffraction, and other factors.
The circle of confusion is a calculation criterion for how much blur is acceptable. It is not an absolute boundary of human vision.
- Model
- Ideal paraxial thin lens — MODEL
- Criterion
- Traditional 30 µm — REFERENCE
- Real lens geometry
- UNKNOWN
This warning appears when the estimated magnification from the ideal thin-lens model is about 0.1× or more. Actual lens magnification varies by lens specification.