Guide-number math, multi-light stop ratios, and shareable diagrams—solved on your iPhone before the stands go up.
Illustrative marketing figures; not App Store metrics.
Gear bay · camera strip · ratio board · falloff playground
Solve distance or f-stop for one head instantly, or drag key/fill/hair/rim chips with stop offsets and live power badges (e.g. key 1/4, fill −1.5). Lock a working camera/ISO/aperture strip so every answer stays session-true.
Onboarding teaches GNs, power fractions, and stop ratios, then drops you into softbox portrait, two-light product, and gelled rim scenes—ready to edit, never empty.
Browse speedlights, monolights, and pack heads with reference GNs, zoom slots, and min/max steps—or add custom heads with your own guide number and power curve.
Pin body label, ISO, target aperture, and shutter ceiling once; every solver and ratio answer stays consistent for the whole session.
Apply softbox, umbrella, beauty dish, grid, gel, or ceiling bounce loss in tenths of a stop; drag subject and wall markers to preview background falloff.
Diagrams, widgets, Shortcuts—offline
Save and duplicate lighting scenes, export image/PDF via Share Sheet, pin WidgetKit power cheat-sheets, and run “Solve flash distance” from Shortcuts—all offline.
Five frames from the flash lab
Portrait, product, and event shooters get reliable guide-number math and multi-light power ratios without napkin guesswork—fully on-device with SwiftData.
BoltRatio Flash Lab is the offline studio flash workbench for portrait, product, and event shooters who are done with napkin math. Build a gear bay of speedlights and monolights, lock a camera/ISO/aperture strip for the session, then solve single-source power or distance in one tap.
Stage key, fill, hair, and rim on a visual ratio board, bake in modifier and bounce loss, scrub inverse-square falloff on a floor plan, and export a clean lighting diagram—fully on-device with SwiftData, seeded pro gear, and demo scenes. No account, no cloud, no spreadsheets on set.