f vs ProFilm Meter

The f-Stop Printing Calculator allows darkroom printers to modify times by stops when calculating exposure values. The calculator will establish 1/4 stop increments (+ or – up to 3/4) of the base time you have entered and, either generate a new time, or an increment of an f-stop if you are burning in. By working with f-stops rather than linear units of time, you can produce an easier to read test strip as the exposure differences are exactly equal. This app has been designed by Digitaltruth Photo Ltd and Bruce Tanner.

ProFilm Meter is the most complete light meter and exposure toolkit for film photographers. From 35mm to 8×10 large format, dry plates to tintypes, it handles every calculation you'd normally reach for three separate tools to solve — all offline, all in real time. LIGHT METERING Your phone's camera becomes a precision reflected-light meter. Choose spot, center-weighted, or average metering and dial in exposure with ⅓-stop, full-stop, or any combination of increment sets running simultaneously. A live RGB histogram keeps highlight and shadow zones in view at all times. Native per-frame ISO, shutter, and aperture capture at ~10 fps Multi-point metering: average 2–4 scene readings into one exposure value Tap-to-focus and multi-lens camera selection Adaptive EV smoothing adjusts for scene changes automatically Screen stays awake during active metering sessions CALIBRATION Two-point guided calibration locks each camera to a trusted reference. After calibration, a fine-tune step lets you match any external meter in ⅓-stop increments. Uncalibrated cameras are gated with a full-screen prompt so you never shoot on an unmeasured body. FILM STOCKS & RECIPROCITY An on-device film stock library covers 35mm, 120, and large format emulsions — including the full Zebra Dry Plate collection. Every stock carries its own reciprocity profile. Eight built-in profiles (Acros II, T-Max, HP5+, Portra, Fomapan, Zebra, and more) plus full custom profile creation, including Schwarzschild p-factor and optional threshold. Add custom film formats and reciprocity profiles inline, without leaving the film stock screen. COMPENSATIONS Reciprocity failure — corrected automatically for exposures beyond threshold Bellows compensation — calculated stop-for-stop from draw and focal length RA4 Color Reversal — estimates scene color temperature and gives you Mired-shift filter corrections for color positives; works in both ambient and flash mode Spectral sensitivity — metering coefficients adjusted for panchromatic, orthochromatic, and blue-sensitive emulsions Lens filters — ND (1–10 stops), polarizer, yellow/orange/red/green contrast filters, R72 and deep IR, plus custom filters Positive/reversal process — +0.5 stop compensation, auto-enabled for tintype stocks UV/environmental compensation — adjustable for altitude and atmospheric conditions IR Light Estimator — dedicated tool for infrared exposure estimation FLASH Flash metering detects incident flash via fast polling with peak-hold and sticky arming. A built-in flash trigger supports Optical Slave (fires the LED torch to trip slaved units) and Cable Sync (audio click for USB-C to PC-sync adapters). VIEWFINDER A lens-independent viewfinder zoom gives consistent framing regardless of which physical lens the phone uses. Overlay your chosen film format frame lines and compose like you're looking through a director's viewfinder. FIELD JOURNAL Save any exposure to the journal with one tap. Each entry records ISO, aperture, shutter speed, EV, reciprocity correction, RA4 and spectral corrections, GPS coordinates, and a cropped preview photo. Entries are exportable and shareable. EXTRA TOOLS Depth of Field Calculator — for any format and focal length Zebra Exposure Guide — zone-system reference for dry plate work Alternative Processes Meter — cyanotype, platinum, salt print, and more Step Wedge Tool — exposure planning for contact printing Rolling Shutter Calculator — flash sync safety for focal-plane shutters 20 FILM FORMATS 35mm · 6×4.5 · 6×6 · 6×7 · 6×9 · 4×5 · 5×7 · 8×10 · 9×12cm · 10×10 · 10×12 · 11×14 · 12×12 · 13×18cm · 20×24 · Sixth Plate · Quarter Plate · Half Plate · Whole Plate · custom dimensions 7 LANGUAGES English · Slovenian · Spanish · French · German · Japanese · Simplified Chinese PRIVACY All metering and calculation runs entirely on-device. No account required. No data leaves your phone.