The Local version of ƒ/Calc allows you to edit the table of imaging areas used in the depth of field, hyperfocal distance, field of view, angles of view, and spot meter viewing angle sections.

To edit the table, simply pull down the list and choose the last item, “Edit...” (This item is not present in the Online version of ƒ/Calc.) This opens a new window showing details about the imaging areas ƒ/Calc knows about. The process of changing the imaging area table is pretty self-explanatory, but there are a few things that require a little explanation.

First, the imaging area dimensions have to be given in millimeters. (ƒ/Calc does all its calculations in millimeters internally.)

Second, you can only have 20 imaging areas defined. There’s no technical reason why ƒ/Calc can’t allow more, but there are good usability arguments against raising the limit. It’s quite unlikely that you use all of the imaging areas that ƒ/Calc comes with, so if you run into this limit, just delete the ones you don’t use to make room for the ones you want to add.

Third, ƒ/Calc currently only supports spherical optics. This means you will get wrong answers if you try to teach ƒ/Calc about things like anamorphic film formats. To support such things, ƒ/Calc’s optics engine will need changes; this is already on the feature wish list.