Photography Calculators

Depth of field, ND filters, timelapse, star trails, field of view, and more. Transparent formulas — learn while you calculate.

Calculate the maximum exposure time for pinpoint stars. The 500 Rule is a quick estimate; the NPF Rule is pixel-level precise.

Camera

Focal (mm)

Aperture

500 Rule

20.8s

500 ÷ (24mm × 1) = 20.8s

NPF Rule (precise)

4.9s

(16.856×f/2.8 + 0.0997×24 + 13.713×5) ÷ 24

NPF accounts for sensor pixel size for maximum precision.

Why show the formulas?

Most calculator apps show you a number. We show you the math. Understanding depth of field, the NPF rule, or ND filter stops makes you a better photographer — not just someone pressing buttons.

All calculations run entirely in your browser. No data is sent to any server. The camera database includes 50 models with verified sensor specifications from manufacturer data sheets.

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