YsEVMeter

YsEVMeter turns your iPhone into a precise three-zone spot light meter for photographers who care about exposure. Point the camera at your scene and read highlight, midtone, and shadow values in real time — then work the way film photographers always have, with the Ansel Adams Zone System built in. METER THE SCENE • Real-time EV metering straight from the live camera • Three-zone spot metering: highlight (red), midtone (green), shadow (blue) • Drag any spot to re-meter, or tap to drop your own custom spots • ISO from 25 to 102400, in color or black & white SEE THE LIGHT • Zone Map overlay posterizes your scene into the 11 Ansel Adams zones (0–X) • Heatmap overlay reveals luminance across the whole frame • Histogram overlay with shadow, midtone, and highlight markers • Adaptive zone detection: 2% percentile, Otsu auto-thresholding, or manual sliders CALCULATE THE EXPOSURE Freeze a snapshot or load a photo from your library (with its EXIF aperture, shutter, and ISO), then solve the exposure: • Aperture f/1–f/64, shutter 1/8000s–480s, EV adjustment ±5 stops • Full-stop or 1/3-stop increments • Color (Wratten) and ND filter compensation • Bellows-extension compensation for large-format work • Reciprocity-failure correction with film-stock presets for long exposures • Smart linking keeps aperture and shutter balanced as you adjust DIAL IT IN • Calibrate against a reference meter for readings you can trust • Frame the shot — preview the exact crop for 35mm, 6×6, 4×5, or a custom format at any focal length, in portrait or landscape • Record exposures to film rolls or quick memos, with optional GPS tagging PRIVATE BY DESIGN Everything runs entirely on your device. No account, no ads, no tracking — your photos and data never leave your iPhone. Made for film shooters, large-format photographers, and anyone learning to see in zones.