Sunny 16 Validation one-tap
One-tap sanity check that compares your meter to the Sunny 16 rule.
Where to find it
Tools tab Sunny 16 Validation
Summary
Sanity-check action: tap once on a sunlit scene that should match the Sunny 16 rule, and the app tells you whether your meter is reading what it should be reading.
How it works
What it does
The Sunny 16 rule says that on a clear sunny day, the correct exposure for a front-lit subject is f/16 at 1/ISO. Tap this validation on such a scene and the app meters it, computes what Sunny 16 predicts for your loaded ISO, and tells you whether your meter agrees.
When to use it
As a sanity check after running calibration, when you are unsure whether your meter readings are honest, or as a quick test before committing to a roll on a tricky day.
What the result means
Within a third of a stop is excellent. Within two-thirds of a stop is normal phone-camera variability and acceptable for negative film. More than a stop off suggests something in the calibration or the scene is wrong (an unusually hazy day, a non-front-lit subject, a phone that needs recalibration).