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All software available from this site, namely Photo Calculator for Windows and Mac, as well as the Sun & Moon Calculator are free.
Just install the latest version over your existing version
The Benefits of a Grey Card
Find out more about grey card and the benefits it can have in photography, including White Balance and Exposure Measurement. See our Benefits of Grey Card
Depth of Field
What is depth of field within photography? Find out more with our Depth of Field in Photography