PROFILM METER
Turn Your Phone into a Precision Light Meter for both Film & Plate Photography
ProFilm Meter turns your phone into a highly accurate light meter engineered for demanding analog workflows. Designed for both modern film and historical processes, it delivers precise exposure readings across materials with different spectral sensitivity modes including blue-sensitive, orthochromatic, and panchromatic. Advanced features such as two-point calibration, reciprocity failure correction, bellows compensation, and real-time colour temperature analysis ensure reliable results in any lighting condition.
Available on Android and IOS
The Complete Light Meter and Photography Toolkit for Film Photographers
Your phone. Your camera. Your film. Complete exposure control.
ProFilm Meter transforms your iOS or Android device into a sophisticated photographic light meter and an extensive toolkit for analog photography. Designed for photographers who demand more than a basic exposure reading, it combines precision light metering, film-specific exposure calculations, camera viewfinder simulation, flash metering, and an extraordinary collection of tools for traditional and alternative photographic processes.
From 35mm street photography to medium and large-format work, from modern film emulsions to historic photographic processes, ProFilm Meter brings the tools of a dedicated photographic studio into the device you already carry.
This isn't simply a light meter. It's a complete photographic companion built around the way film photographers actually work.
PRECISION LIGHT METERING
More control. Better information. Greater confidence.
At its core, ProFilm Meter provides a highly configurable reflected-light meter designed to give you control over how you measure a scene and determine exposure.
Choose from four metering methods:
Spot Metering: Measure a specific area of your subject.
Center-Weighted Metering: Give greater importance to the center of the frame.
Average Metering: Evaluate the overall scene.
Multi-Point Metering: Take two to four individual readings and combine them into an averaged exposure value.
Adjust the sampling area and center weighting to suit your subject and shooting conditions.
Take control of every exposure variable with adjustable ISO, aperture, shutter speed, and exposure compensation. Enter standard or custom ISO values, including fractional values, and choose the exposure increments that match your camera and working preferences.
Work in full manual mode, aperture priority, or shutter priority. Let the meter calculate the corresponding shutter speed or aperture, lock a reading when you need to study it, and return to live metering whenever you're ready.
Additional metering information includes:
Live Exposure Value (EV) calculations.
Optional real-time RGB histogram.
Live estimated Kelvin color temperature.
Adjustable 1/3, 1/2, 2/3, and full-stop increments.
Multiple increment sets that can be combined.
Exposure reading lock and review.
Calibrate the meter to your equipment
Every phone camera and lens combination behaves differently. ProFilm Meter includes a guided two-point calibration process that allows you to compensate for your device's individual characteristics.
Calibrate against dark and bright reference levels, then fine-tune the results against a trusted reference light meter when desired.
The result is a meter tailored to your equipment rather than relying entirely on generic smartphone camera behavior.
A VIEWFINDER FOR YOUR FILM CAMERA
See your composition before you take the photograph.
ProFilm Meter goes beyond measuring light. Its integrated viewfinder lets you preview how your film camera will frame a scene using your selected film format and focal length.
Choose from a wide range of built-in photographic formats, including:
35mm film formats.
Medium-format systems.
Large-format sheet film.
Instant film formats.
Historical and specialty plate formats.
Custom formats with user-defined dimensions.
Select your focal length, adjust framing, and switch between portrait and landscape orientation.
Composition overlays include:
Frame Lines.
Rule of Thirds.
Golden Ratio.
Crosshair.
Adjust frame margins to better represent your camera's actual framing.
On supported devices, you can tap the viewfinder to request camera focus at a selected point, lock the preview, and use the Viewfinder Zoom Slider to change focal length and framing while the viewfinder and metering update together.
Multiple phone camera lenses
On supported iOS and Android devices, select from recognized rear-camera lenses, including main/wide, ultra-wide, and telephoto cameras where available.
Automatic lens selection can switch between recognized and calibrated options as appropriate.
You can also adjust the phone camera's equivalent focal length and viewfinder frame-line margin to better match your camera's actual field of view.
These adjustments are separate from light-meter calibration, allowing you to fine-tune composition without changing your exposure calibration.
Build your own lens catalog
Create a Personal Lens Catalog containing your actual photographic equipment.
Define individual lenses with:
Focal length.
Film format or image-circle coverage.
Available aperture markings.
Mechanical shutter speeds.
UV-glass information.
For catalog lenses with mechanical shutters, ProFilm Meter can match calculated exposures to the shutter speeds marked on your lens.
When the ideal exposure is longer than the slowest available shutter marking, the app displays the required duration so you can use Bulb exposure where appropriate.
BUILT AROUND FILM
Exposure calculations that understand the materials you're using.
Digital exposure meters generally stop at ISO, aperture, and shutter speed. Film photography requires considerably more information.
ProFilm Meter incorporates film-specific calculations and corrections to help you account for the characteristics of the materials, cameras, and processes you use.
Film stocks and custom profiles
Choose from built-in film stocks, browse remote stock catalogs, including Zebra Dry Plates, or create your own custom film profiles.
Customize film information, ISO, spectral sensitivity, reciprocity behavior, and correction thresholds.
You can also create and edit custom film formats and reciprocity profiles.
Reciprocity failure compensation
Long exposures require special consideration because film does not always respond linearly to extended exposure times.
ProFilm Meter supports stock-specific reciprocity profiles and customizable Schwarzschild p-factors and exposure thresholds.
When a film profile is selected, the app can automatically calculate the corrected exposure duration for long exposures.
You can also use the standalone Reciprocity Calculator for custom calculations and comparisons.
Filter compensation
Apply exposure factors for a wide selection of photographic filters, including:
Neutral Density (ND).
Polarizing filters.
Yellow filters.
Orange filters.
Red filters.
Green filters.
Infrared filters.
Custom filters.
Filter corrections can be incorporated into your exposure calculations rather than requiring you to work everything out separately.
Large-format and specialized corrections
ProFilm Meter includes additional compensation tools for specialized photographic workflows:
Bellows Extension Compensation: Calculate the exposure increase required when extending your lens for close focusing and large-format photography.
Spectral Sensitivity: Select panchromatic, orthochromatic, or blue-sensitive film response modes.
Positive Exposure Adjustment: Apply the additional +0.5-stop adjustment for reversal processes.
Environmental Compensation: Account for UV conditions and elevation using live environmental information, manual UV adjustments, or offline location and elevation estimates.
UV Transmission Compensation: Scale UV corrections for UV-sensitive materials according to lens coating characteristics or known UV transmission.
These features make ProFilm Meter particularly useful for photographers working with historical processes, specialized emulsions, and large-format equipment.
ADVANCED COLOR AND INFRARED TOOLS
RA4 Color Reversal
The RA4 Color Reversal tool analyzes scene color information and provides suggested color filtration packs to help establish a starting point for color reversal printing.
Separate analysis is available for flash readings, allowing you to evaluate the color characteristics of flash illumination as well as ambient light.
Infrared Light Estimator
Working with infrared film and filters introduces exposure considerations that conventional meters cannot address.
The IR Light Estimator evaluates current scene conditions and helps estimate infrared exposure adjustments using 720nm and 850nm filter settings.
These tools provide practical starting points for specialized work, reducing the need to rely entirely on guesswork and extensive exposure bracketing.
PROFESSIONAL FLASH METERING
Bring flash exposure into your workflow.
ProFilm Meter includes flash-metering capabilities for photographers working with studio flash, portable strobes, and other electronic flash systems.
Hold an ambient-light reference, fire your flash, and capture the flash peak. The app displays the flash reading alongside the ambient exposure so you can understand the contribution of each light source.
Adjust flash sensitivity and flash-only EV compensation, and account for camera ND filters when flash output is too bright for the phone camera to capture reliably.
You can meter flash manually using your camera, hot shoe, or compatible radio trigger.
Optical slave flash triggering
Use your phone's rear LED to trigger compatible optical-slave flashes.
Adjust the LED pulse duration to accommodate different flash systems and triggering requirements.
Android hardware light sensor
Supported Android devices can use their hardware ambient-light sensor to detect flash output. This method is not available on iOS.
Experimental Cable Sync
For photographers who want a direct flash-sync workflow, ProFilm Meter includes an experimental Cable Sync feature that uses an audio waveform to trigger compatible external flash equipment.
Adjust waveform characteristics and pulse duration to suit your hardware.
Important: Cable Sync requires a properly rated optoisolator between the phone and flash-sync connection. Never connect a phone directly to a flash-sync port. Compatibility depends on the phone, audio adapter, isolation circuit, and flash equipment.
YOUR EXPOSURE JOURNAL
Record every exposure. Revisit every decision.
ProFilm Meter includes a Field Journal that allows you to save and review your photographic exposures.
Each saved entry can contain:
ISO, aperture, and shutter speed.
Exposure Value (EV).
Film stock and format.
Focal length.
Metering mode.
Applied exposure corrections.
Notes and observations.
Location information, when recorded.
An optional viewfinder photograph.
Saved multi-point readings can be inspected individually, and correction indicators help you understand which adjustments were applied to the final exposure.
Export and share your work
Export individual journal entries as composite JPEG images containing your exposure information.
When EXIF embedding succeeds, exported images can include exposure data and recorded coordinates. Images can still be saved and shared if metadata embedding is unsuccessful.
Save journal photographs individually or in bulk to your device's photo library, or enable automatic gallery saving on supported iOS and Android devices.
Preferred Setups
Save frequently used combinations of film, exposure settings, lenses, and process configurations as Preferred Setups.
Instead of rebuilding your configuration every time you change cameras or film stocks, recall your saved setup and get back to photographing.
Settings Transfer
Move selected settings and equipment configurations between devices using the .profilm export and import system.
Settings Transfer can include your selected gear and application settings. Journal entries, photographs, and device-specific camera and light-meter calibration are not included.
AN ENTIRE DARKROOM AND FIELD TOOLKIT
More than a light meter. A collection of specialized photographic instruments.
ProFilm Meter includes a growing collection of additional tools for traditional photography, large-format work, alternative processes, and darkroom experimentation.
Exposure and photographic calculators
Zone System
Place a subject tone within the Zone System using single-point or two-point placement. Calculate the resulting exposure adjustment and apply it to your metering workflow.
Depth of Field Calculator
Calculate near and far focus limits, total depth of field, and hyperfocal distance using your selected format, focal length, and aperture.
Reciprocity Calculator
Calculate corrected long-exposure times using built-in film profiles or custom Schwarzschild p-factors and thresholds.
Equivalent Lens Calculator
Compare focal lengths and angles of view across different film formats using the 35mm format as a reference.
Pinhole Calculator
Calculate effective f-stop, pinhole diameter, focal distance, and image-circle coverage for pinhole camera construction and exposure planning.
Flash Guide Number Calculator
Calculate flash distance or required aperture using guide number, ISO, and flash power.
Rolling Shutter Calculator
Determine suitable shutter timing by matching a locked exposure duration to tension-and-aperture combinations. Includes built-in and custom focal-plane camera profiles.
Custom Shutter Speeds
Create and save named, non-standard shutter-speed presets. The meter can display the nearest matching preset when calculating exposure.
Historical and alternative photographic processes
Zebra Exposure Guide
Access historical Zebra Dry Plates exposure charts and create in-camera exposure test strips for experimental and historical photographic work.
Alternative Processes Meter
Calculate estimated exposure times for a range of alternative photographic printing processes, including:
Cyanotype.
Salt Printing.
Platinum/Palladium.
Van Dyke Brown.
Kallitype.
Gum Bichromate.
Choose between sunlight and indoor UV light sources, fine-tune exposure for your particular process, and account for glass in the printing path.
Negative Density Reader
Measure the transmission density of photographic negatives against a sampled screen baseline.
Wet Plate Timer
Estimate and count down the working window for wet plate collodion photography using temperature, humidity, elevation, and wind conditions.
Step Wedge Tool
Plan timed exposure sequences for camera testing, contact-print calibration, and alternative-process experiments.
Additional advanced tools
ProFilm Meter also offers additional unlockable tools for photographers who want to expand their workflow:
Parallax Calculator: Additional planning support for photographic equipment and camera positioning.
Large-Format Movements: Calculate and preview large-format camera movements using an integrated viewfinder overlay.
Scene Dynamic Range Indicator: Evaluate scene brightness range to help assess exposure and tonal conditions.
Exposure Countdown Timer
Use the integrated countdown timer to time locked exposures, including reciprocity-corrected exposure durations when applicable.
MAKE IT YOUR OWN
Your equipment. Your workflow. Your preferences.
No two photographers work exactly alike. ProFilm Meter provides extensive customization so you can configure the application around your cameras, lenses, films, and photographic processes.
Manage your own libraries of:
Film stocks.
Reciprocity profiles.
Film formats.
Focal lengths.
Personal lenses.
Aperture series.
ISO values.
Shutter-speed presets.
RA4 papers and filters.
Customize the meter toolbar, show or hide optional tools, and save named Preferred Setups for different cameras and photographic workflows.
Additional application settings include:
Keep the screen awake while metering.
Metric or imperial measurements.
Light or dark appearance.
Seven available languages: English, Slovenian, Spanish, French, German, Japanese, and Simplified Chinese.
DESIGNED FOR THE FIELD AND THE DARKROOM
ProFilm Meter is available for both iOS and Android.
Its core metering and exposure calculations work offline, making it useful in the field, studio, or darkroom without requiring a continuous internet connection.
Additional connectivity features include:
Live environmental information for UV and elevation compensation.
Offline UV estimates using location and saved elevation information.
Remote film-stock and filter catalogs, with local caching.
Settings export and import.
Live environmental requests use Open-Meteo, while remote stock and filter catalogs are retrieved from GitHub.
Camera lens selection and hardware capabilities vary by device. Android hardware light-sensor flash detection is not available on iOS. Experimental Cable Sync requires compatible, properly isolated external hardware.
Exposure corrections and environmental estimates are intended as practical starting points. Actual results can vary depending on film characteristics, photographic materials, equipment, and environmental conditions.
ONE APP. AN ENTIRE PHOTOGRAPHIC WORKFLOW.
Whether you're metering a portrait on 35mm film, calculating reciprocity for a long-exposure landscape, composing a 4×5 image, working with a mechanical large-format lens, metering studio flash, or calculating exposure for a cyanotype print, ProFilm Meter puts the tools you need within reach.
It brings together the precision of a dedicated light meter, the flexibility of a photographic viewfinder, the calculations required for film photography, and a collection of specialized tools for traditional and experimental processes.
Built for film photographers. Designed for creative control. Made for the way you photograph.
Take control of your exposure.
Discover what ProFilm Meter can do for your photography.
Available for iOS and Android.
Instructions to build your own Camera to flash sync cable
Warning, if you mess this up you may destroy your phone. If you do it is on you
This is for using your phone to trigger your flash VIA a USBC to 3.5mm headphone jack. For my google pixel 9 using the Sine waveform and 500ms Burst Length, Flash Sensitivity at 1.08 with a flash duration that matches the flash in use this works well. On my Ipad pro with the same dongle a Square waveform works best. I have tested a bunch of different dongles and you get what you pay for as the cheap ones tend to be less reliable. In short you will have to play with it to figure out what settings work best with your hardware.
SIMPLE USB-POWERED FLASH TRIGGER
=================================
USB 5V POWER
------------
USB +5V
|
|
R3 680Ω
|
|
PC817 Pin 1 (LED +)
PC817 Pin 2 (LED -)
|
Collector
2N3904
|
Emitter
|
+-------------------- GND
|
USB Ground
|
+-------------------- Phone Sleeve
PHONE AUDIO INPUT
-----------------
Phone Tip
|
|
C1 10µF
(+ toward phone)
|
+------ R1 1kΩ ------ Base (2N3904)
|
R2
10kΩ
|
GND
OPTIONAL STABILITY CAPACITOR
----------------------------
Base (2N3904)
|
C2 1µF
|
GND
FLASH CONNECTION
----------------
PC817 Pin 4 -------- PC Sync Center
PC817 Pin 3 -------- PC Sync Shell
USB NOISE FILTER (recommended)
--------------------------------
+5V USB
|
100µF
|
GND
and also add:
+5V USB
|
0.1µF
|
GND
Important Notes
Electrolytic Capacitor Orientation
C1
Positive side → Phone
Negative side → transistor base network
100µF USB filter capacitor
Positive → +5V
Negative → GND
| Part | Value |
| ------------- | ----------------- |
| Q1 | 2N3904 or BC547 |
| Optocoupler | PC817 or PC817C |
| R1 | 1kΩ |
| R2 | 10kΩ |
| R3 | 680Ω |
| C1 | 10µF electrolytic |
| C2 (optional) | 1µF |
| Supply filter | 100µF + 0.1µF |