# Zone Tool — Zone system calculator

> Zone system calculator for photographic exposure and development adjustments. (iPhone/iPad app by Jouni Erola.)

- Source: https://appshunter.io/ios/app/zone-tool/id1489637620 (this page in markdown: same URL + `.md`)
- Developer: [Jouni Erola](https://appshunter.io/developer/295758397)
- Category: Photo & Video, Utilities
- Price: $0.99
- Rating: 2.80/5 from 6 App Store ratings · 1 written reviews indexed
- Age rating: 4+
- Requires: iOS 12.2 · 0 MB
- Languages: American English
- Released: 2019-11-29
- Data updated: 2026-08-24
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/zone-tool/id1489637620/reviews.md

## What is Zone Tool?

With this tool you can calculate your exposure and needed adjustment for development. It uses zone system theory originally invented by Ansel Adams and Fred Archer.

First decide zone of your shadows and measure the shadows. Then device highlight zone and measure the highlights. Measure these with the film ISO you are going to use. You also need to decide shutter speed in beforehand.

The app calculates exposure aperture for you and also tells if you need to shorten (N+..) or expand (N-..) your development time.

You will get best results with a spot light meter but mobile apps will probably do fine.

## Key features

- Zone system exposure calculation
- Shadow and highlight measurement
- Film ISO input
- Shutter speed adjustment
- Development time calculation
- Aperture determination

## Chart rankings

- #99 in Top Paid · Photo & Video (US App Store)

## Recent user reviews (1 of 1)

All indexed reviews: https://appshunter.io/ios/app/zone-tool/id1489637620/reviews.md

### 4/5 — Pretty good overall

*2022-02-21*

If it is possible, adding the adjustment for shutter speed instead of only the aperture will be so much helpful.

## Frequently asked questions about Zone Tool

### What is Zone Tool used for?

Zone Tool is used to calculate photographic exposure and development adjustments based on the zone system theory. It helps photographers determine the correct aperture and development time for their film.

### How does Zone Tool work?

You input your desired shadow and highlight zones, measure them with your film's ISO, and set your intended shutter speed. The app then calculates the necessary aperture and tells you if development time needs to be shortened or expanded.

### Does Zone Tool require a specific type of light meter?

While best results are achieved with a spot light meter, the app suggests that mobile apps should also work adequately for measurements.

### What is the price of Zone Tool?

Zone Tool is a paid application, available for $0.99.

### On which devices can I use Zone Tool?

Zone Tool is supported on iPhone and iPod devices.

### How often is Zone Tool updated?

The latest version, 1.2, was released on March 3, 2026, indicating a potential update schedule, though the last update was in 2019.

### What is the age rating for Zone Tool?

Zone Tool has an age rating of 4+, making it suitable for a wide range of users.

### Does Zone Tool have ads?

No, Zone Tool does not contain advertisements.

## Version history (last 3 releases)

### 1.2 — 2026-03-03

Bugfixes

### 1.1 — 2019-12-01

Fixed N calculation (was reversed)
Added developing tip text

### 1.0 — 2019-11-29

No release notes.

## More apps by Jouni Erola

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- [tykki](https://appshunter.io/ios/app/tykki/id1278311224)
- [sequle](https://appshunter.io/ios/app/sequle/id1313318732)
- [Visits HTTP](https://appshunter.io/ios/app/visits-http/id1471966206)

All apps by Jouni Erola: https://appshunter.io/developer/295758397

## Related topics

[ansel](https://appshunter.io/ios/topics/ansel)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-24.*