Calculation methodology

Apertally calculators are designed for planning, comparison and field preparation. We publish the core formula, identify significant assumptions and separate mathematical output from equipment-specific guarantees.

Source hierarchy

We prioritise recognised standards bodies, manufacturer documentation and established optical, geometric or exposure relationships. Secondary explanations may provide context, but do not replace an authoritative specification when one is available.

Calculation design

Inputs are expressed in units photographers and filmmakers commonly encounter. Conversions are performed before the central formula is applied, and results are rounded only for presentation. Where practical uncertainty is material—such as formatted card capacity or real lens behaviour—we state it alongside the result.

Verification

Each calculator is checked against hand-worked examples and boundary cases before publication. We also compare representative outputs with documented examples or independent calculations where appropriate. A correct formula can still be unsuitable for a particular camera mode, so manufacturer guidance remains the final authority for compatibility.

Limits of the models

Depth of field depends on an acceptable-blur convention; field of view can differ because of distortion correction and focus breathing; storage varies with codec behaviour and file-system overhead. Apertally presents these figures as informed estimates, not guaranteed measurements.

Updates and corrections

We review material when standards, manufacturer guidance or better evidence changes. Substantial editorial revisions are reflected in the review date. Suspected errors can be reported through our contact page.