October 21, 2026
Using a phone light meter for film photography
A practical way to choose exposure settings when your film camera has no working meter.
An older film camera may have no light meter, or one you no longer trust. A phone can give you a useful starting point for exposure. Here’s the short version of how to use it.
Start with the film speed
Set the meter to the ISO of the film in your camera. The ISO setting tells the meter what sensitivity to calculate for. If you are deliberately rating the film at a different speed, use that value instead and keep it consistent for the roll.
Read the scene, then choose a pair
Point the phone at the part of the scene you care about. The meter gives you combinations of shutter speed and aperture for that reading. Pick a pair your camera can use.
A faster shutter speed helps with movement, while a wider aperture lets in more light and changes depth of field. You can move between equivalent pairs without changing the overall exposure.
Check what the meter is looking at
A bright sky behind a darker subject can pull the reading away from the subject. Move closer or meter a part of the scene with similar light, then decide whether to add exposure compensation. When the light changes, take another reading.
Phone cameras and dedicated light meters can disagree. Before relying on a phone for an important roll, compare a few readings with a meter or camera you trust.
An Android app for this
I made Exposure — Light Meter for exactly this kind of quick reading. Set the film ISO, view shutter and aperture pairs, use exposure compensation when needed, and pause the reading while you set your camera. It works offline. You can get it on Google Play or read more on its project page below.