Methodology - how Photo-Calc calculates results
Every result on Photo-Calc comes from the standard optical and photographic formulas, computed in your browser with no rounding shortcuts. This page lists the formula behind each calculator so you can check our work - transparency matters for a tool people rely on.
Depth-of-field and hyperfocal results use the circle of confusion for your selected sensor. Field-of-view and crop-factor results use each format's real sensor dimensions. Golden-hour times use a standard solar-position algorithm from your coordinates and date, shown in your device's local time zone. Where a rule is an approximation - like the 500 rule for stars - we say so and offer a stricter alternative.
Formula
| Depth of Field Calculator | H = f² / (N · c) + f |
|---|---|
| Hyperfocal Distance Calculator | H = f² / (N · c) + f |
| Field of View Calculator | AoV = 2 · arctan( d / (2f) ) |
| Crop Factor Calculator | f_equiv = f × crop |
| Aspect Ratio Calculator | ratio = W : H (divided by GCD) |
| Print Size Calculator | size = pixels ÷ DPI |
| 500 Rule Calculator | t_max = 500 / (f × crop) |
| ND Filter Calculator | t_new = t × 2^stops |
| Time-lapse Calculator | clip = (duration ÷ interval) ÷ fps |
| Exposure Calculator | EV = log₂(N² / t) − log₂(ISO / 100) |
| Sunny 16 Calculator | t = N² / (2^EV × ISO/100) |
| Flash Guide Number Calculator | distance = GN / N × √(ISO / 100) |
| Golden Hour Calculator | sun altitude h(t) from date, latitude and longitude |