Precision Light Metering
专业测光
Professional-grade exposure measurement calibrated for film photography
FilmMeter transforms your iPhone into a professional-grade reflected light meter purpose-built for film photography. Using Apple’s AVFoundation framework, the app reads real-time luminance data from the iPhone camera sensor and converts it into precise exposure values (EV) calibrated for analog film stocks. Unlike digital camera metering that targets 18% gray for a digital sensor’s linear response, FilmMeter accounts for the unique tonal response curves of silver halide emulsions, giving you exposures that preserve shadow detail and highlight texture on film.
The exposure calculator supports 1/3 stop, 1/2 stop, and full stop increments for aperture, shutter speed, and ISO – matching the click-stop precision of professional film cameras from Nikon, Canon, Leica, and Hasselblad. Whether you are shooting wide open at f/1.4 for shallow depth of field portraits or stopped down to f/16 for landscape hyperfocal sharpness, FilmMeter displays the complete exposure triangle in a clean, readable interface. Lock any one variable and the app instantly recalculates the other two, letting you prioritize depth of field, motion blur, or film grain as your creative vision demands.
Long Exposure Timer and Reciprocity Compensation
For exposures beyond one second, FilmMeter includes a built-in countdown timer with audible and haptic alerts. Long exposure film photography requires reciprocity failure compensation because film emulsions lose sensitivity during extended exposures. FilmMeter automatically calculates the corrected exposure time based on each film stock’s unique reciprocity characteristics – Fuji Acros 100 barely needs correction up to two minutes, while Ilford FP4+ may require doubling or tripling the metered time. The timer counts down the compensated duration so you can focus on your composition instead of mental math.
Scene-Aware Metering with AI
FilmMeter goes beyond simple reflected metering with its AI scene detection system. The hybrid histogram and machine learning analysis identifies challenging lighting situations – backlit subjects, snow scenes, night cityscapes, high-contrast stage lighting – and suggests EV compensation adjustments before you press the shutter. This intelligence is especially valuable for slide film shooters where exposure latitude is measured in fractions of a stop.
Complete Exposure Workflow
The light meter integrates seamlessly with FilmMeter’s depth of field calculator and LiDAR rangefinder, providing a complete exposure and focus solution in one app. Combined with film roll management, every metered reading can be recorded alongside your shot notes for a complete shooting log. Browse the film stocks database to see which films are supported with automatic reciprocity compensation and LUT color previews.