Focus, Depth of Field, and Macro

What focus distance and aperture cover my scene?

Solve near and far depth-of-field limits from your focal length, aperture, focus distance, and circle-of-confusion criterion, or find the smallest aperture that covers a stated interval.

Answer

Ready

Focal length (mm)

Aperture (f-number)

Focus distance (m)

Circle of confusion (mm)

Critical near distance (m, optional)

Critical far distance (m, optional)

Next decision: Diffraction and Sampling Tradeoff Planner

Visualize

Calculate to see the focus-zone diagram.

Quantity	Value

Compare

Aperture	Near limit	Far limit

Stress-test

Plan

Calculate a result to generate a copyable plan.

Understand depth of field as a chosen criterion

Depth of field is the range of object distances that stay within a chosen acceptable blur limit. It is useful for planning a near-to-far subject interval, but it is not a promise that every part of a real photograph will look sharp. Focus accuracy, subject movement, camera movement, lens behavior, processing, crop, output size, and viewing distance all remain part of the result.

This planner makes the blur criterion visible through the circle of confusion. The circle of confusion is an allowed diameter on the image plane, not a physical fact about the subject. A larger final print or closer viewing can require a stricter criterion. That is why a fixed number such as 0.03 mm can be a starting convention for a 35 mm example but cannot be a universal answer for every sensor and output.

Enter the focal length, aperture, focus distance, and the criterion you intend to use. The calculated near and far limits show whether a specific foreground-to-background interval is covered. For a 50 mm lens at f/8, focused at 5 m with a 0.03 mm criterion, the calculated zone is about 3.39 m to 9.44 m. A subject at 10 m is outside that defined interval even though it may still look acceptable in a small display.

Use the target range when the real decision is coverage. The planner can find the smallest aperture in its supported range that covers the entered near and far distances at the focus distance you chose. That answer carries a tradeoff: stopping down can increase depth of field while changing exposure and making diffraction more relevant for fine output. Compare one stop either side, then decide whether more depth, a faster shutter, or lower ISO is the scarce resource.

Leave margin. A calculated boundary is not a place to put a critical eye, flower edge, or foreground detail when the subject can move or focus can shift. For landscapes, use the hyperfocal-focused engine when infinity is part of the composition. For magnified close-up work, use the macro planner instead, because ordinary distance approximations become less dependable.

FAQ

Why does circle of confusion matter?: It defines the acceptable blur threshold used to calculate near and far limits. Different output and viewing conditions can justify different thresholds.
Does f/16 always give more usable depth?: It usually enlarges the calculated zone under the same criterion, but it also changes exposure and can make diffraction more relevant.
Can I put the focus point exactly at the calculated boundary?: You can, but a critical subject detail needs margin for focus error, movement, and changed viewing conditions.