Film Spot Meter

An averaging meter reads the whole frame and splits the difference. Film Spot Meter reads only the area inside the spot circle, so you decide exactly which part of the scene sets the exposure: a face in shade, a backlit leaf, the detail you want to hold in a shadow. Tap Hold to lock the reading, then lower the phone and set your camera.

Choose an aperture and get a shutter time, or choose a time and get an aperture. Long exposures are shown exactly, such as 1m 47s, so you can time them by hand.

A plain meter reading puts whatever you metered on Zone V, middle gray. Film Spot Meter lets you place it on any zone instead: light skin on Zone VI, or snow with texture on Zone VIII.

For full Zone System work, record a shadow and a highlight. The app sets the exposure from the shadow, shows the scene’s brightness range in stops, and tells you the development to bring the highlight where you want it: N, N+1, N−1 and so on. With only a highlight recorded, it exposes for the highlight instead, which suits slide film.

Zone view colors the live picture by the zone each area will print on, so you can see where the whole scene falls before you expose.

New to it? Read the Zone System guide.

Once exposures run past about a second, film needs more time than the meter says, so a metered 10 seconds may need 20 or more. This is reciprocity failure, and it’s the usual reason night shots and dim interiors come back thin.

Choose your film and the app corrects the time for you. Built-in films:

• Ilford Pan F+
• Ilford FP4+
• Ilford HP5+
• Ilford Delta range
• Ilford SFX
• Ilford XP2
• Kodak Tri-X
• Kodak T-Max 100
• Kodak T-Max 400
• Fujifilm Acros II

For anything else, enter the exponent from the film’s data sheet.

More in Reciprocity failure explained.

When you focus close with a view camera, a bellows, or extension tubes, the lens moves farther from the film and less light reaches it. At life size you lose 2 full stops. Enter the focal length and bellows draw, and the app shows the exposure factor, the stops of correction, and the magnification, then builds the correction into the result.

More in Large format movements and bellows factor.

Switch to Manual EV to enter a light level yourself, for example EV 15 for bright sun. The zone system, bellows and reciprocity all work the same way. A one-time calibration against a meter you trust keeps camera readings accurate.