PhotoPrepHow it works
Start with a metered shutter time, aperture and ISO. Target shutter time equals source time × aperture ratio squared × source ISO / target ISO × 2 to the power of added ND stops. The nominal camera setting is approximate; its rounding difference is shown. This is not a light meter and does not account for flash or film reciprocity failure.
Example
Changing f/4 to f/8 at ISO 100 turns 1/125 s into 0.032 s. A camera setting of 1/30 s is close, with a small rounding difference. Adding six stops of ND multiplies the calculated time by 64. Equivalent brightness can still change motion blur, depth of field and noise.
References
Edmund Optics — Focal length and field of view · Nikon — Exposure · Cambridge in Colour — Depth of field
Frequently asked questions
How accurate are the calculations?
Enter focal length in millimetres, aperture, circle of confusion and subject distance. This thin-lens model estimates acceptable sharpness rather than a hard boundary. A smaller circle of confusion demands stricter sharpness. Distances are measured from the lens principal plane; macro magnification, pupil ratio, diffraction and lens-specific behavior are excluded.
Where is my shot list stored?
Create an establishing view, a main subject and a detail shot. Load example appends three editable shots. Up to 200 shots are saved in this browser; changing devices or clearing browser data will not preserve them. Export regularly if the plan matters.