ExpoDev App ExpoDev App ExpoDev App ExpoDev App ExpoDev App ExpoDev App

BTZS meets the iPhone. It's the perfect match of Phil Davis' BTZS with the same device that the rest of my life is on. No more carrying multiple gizmos around with me to calculate my exposures and development times. I'm loving it.

Robert Levittan

Powerful, comprehensive, and a snap to use in the field, the ExpoDev App multiplied my confidence that I’d get the optimum negative under the most dire of conditions. ... a tool that spells liberation for the traditional film photographer.

Bill Waldron

ExpoDev is truly a remarkable tool to have in the field... It has liberated me from having to worry about my negatives, so that I can direct my attention to the important process of making a photograph.

Laura Campbell

BTZS Expo/Dev App is a great tool... for the price of a lunch and a couple of days of film testing you can have perfect exposures every time. BTZS is a godsend and a no brainer for any serious large format photographer.


BTZS ExpoDev for iOS

BTZS ExpoDev is the newest generation of ExpoDev for Apple iOS devices. As a companion app for BTZS Plotter, ExpoDev allows you to use your BTZS Film Profiles to accurately calculate B&W film exposures in the field for consistently exposed negatives that are easier to print in the darkroom. ExpoDev was designed for Large Format film photographers working in any traditional or alternative process (including hybrid processes such as film scanning/digital printing).

Available on iTunes


  • Interactively calculates the SBR, Average Gradient, and the EFS for each scene while metering
  • Supports both BTZS Incident and Zone System metering
  • Sophisticated reciprocity failure adjustments for both exposure and development time that are based on lab-quality test data for over 90 film and developer combinations
  • A 3-mode Depth of Field calculator (Aperture/Distance, Near/Far Distances, and Focus Rail Spread) with selectable Circle of Confusion size
  • Managed lists of Film Profiles, lenses, and filters
  • Exposure record keeping system
  • Determines exposure by selecting either the Aperture or Shutter speed to use
  • Supports Apertures up to f/2048 (perfect for pinhole work) and Shutter speeds up to 6 hours
  • An integrated exposure timer than can time exposures up to 12 hours
  • and more...


Please visit ViewCameraStore.com for information on their BTZS Film Testing services.