Zone Tool
Jouni Erola
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.
Download price in United States
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In-app purchases in United States
Items currently visible on Apple’s public App Store page. This may not be the complete App Store Connect catalog.
Source: Apple public App Store page · Publicly visible items only · Checked Aug 4, 2026
About Zone ToolStorefront description supplied by Apple.
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.
Frequently asked questions
Quick answers based on the latest observed App Store data.
How much does Zone Tool cost in United States?
The latest observed download price is $0.99. Open the official App Store link to confirm the current checkout price.
Does Zone Tool have in-app purchases?
Apple's public page currently shows 0 purchase items in this storefront. The public list may be incomplete.
Can the price differ by country?
Yes. App Store prices can vary by storefront, currency, taxes, and developer pricing. We currently have 1 regional observations.