Practise the Zone System on your phone
Adams-and-Archer placement and fall, multi-spot biasing, and development decisions made visible. For beginners and seasoned printers alike.
What the Zone System actually is
The Zone System is a way of mapping every tone in a scene onto a scale from zone 0 (pure black) to zone X (pure white), with zone V being middle grey. A reflective meter reads middle grey, so any single reading places that tone on zone V by default. The Zone System lets you choose a different placement: read a highlight, place it on zone VIII, and the exposure follows so that the highlight prints as a textured light grey instead of as middle grey.
Once a tone is placed, every other tone in the scene falls onto a specific zone as a mathematical consequence. The fall is what tells you whether the scene will fit on the film.
How Zone Light Meter implements placement and fall
Open the viewfinder. Spot-meter a tone that matters (a highlight, a face, a deep shadow). Tap the placement control and pick the zone you want that tone to land on. The app re-derives the exposure for that placement and shows the full 0-10 scale with every visible tone marked.
If your shadows would fall on zone I (no detail) and your highlights on zone IX (no detail), the scene exceeds the latitude of the film and you need to decide what to sacrifice. Negative film: expose for the shadows, develop for the highlights. Slide film: expose for the highlights, accept the shadows. Either way, the placement makes the decision visible before you trip the shutter.
Multi-spot with bias
For portraits and studio work, a single reading on a single tone is not enough. Multi-spot lets you take three or more readings and bias them by importance. A typical portrait: two readings on the face, one on the brightest highlight, weighted with the face at 70 percent and the highlight at 30 percent. The app averages with bias and produces the exposure that protects the tones you care about.
From placement to development
Adams's "expose for the shadows, develop for the highlights" is a development decision. If your scene contracted (shadows on zone IV, highlights on zone V), you need to expand development (N+1 or N+2) to push the highlights higher. If the scene expanded (shadows on zone II, highlights on zone X), you need to contract development (N-1 or N-2) to pull the highlights back.
Zone Light Meter shows the contrast range of the scene in stops and suggests development direction based on the range. The shot log captures both your placement and your intended development so when you process the roll you know what each frame was asking for.
For beginners
You do not need to understand any of this on day one. The app works as a simple averaging meter for as long as you want. When you start wondering "why did my highlights blow out" or "why is the shadow muddy", the Zone System tools are there to answer.
The glossary entry for the Zone System has a plain-language intro with photos. Several documentation pages walk through worked examples from real scenes.
FAQ
Do I need to know the Zone System before using Zone Light Meter?
No. The app teaches it as you shoot. You can use the meter as a simple averaging meter on day one and adopt the Zone System workflow when you are ready. The glossary entry for Zone System has a plain-language intro.
Which app screen shows the zone overlay?
The viewfinder. Tap a tone to spot-meter it, then place that reading on a zone with the placement control. The app shows the full 0-10 scale with each visible tone in the scene mapped onto it.
Does it support placement and fall?
Yes. Placement is what you choose (this highlight is zone VIII). Fall is what happens to every other tone in the scene as a consequence. The app shows both: you place, you see the fall, you decide development.
Can I bias multi-spot readings by importance?
Yes. Take three or more spot readings, weight them by importance (a face matters more than the wall behind it), and the app produces a single bias-weighted exposure recommendation. This is how studio and portrait workflows actually work.
Learn more
Read the glossary entry for the Zone System, or browse the dedicated section of the documentation.