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Focal Length, Depth of Field, and Field of View

Focal Length, Field of View and Depth of Field… These all sound very exciting. Or maybe not. Perhaps they just sound slightly frightening. They are the sort of thing that you can delve into in quite some complexity, or try to avoid as much as possible, but you need to know a little about them if you are to use your cameras to their fullest capacity.

What this page will do is give you some tools to think about questions like ‘how far to I have to stand back to fit everyone in?’ and how close can I focus with this particular camera?’

Focal Length

The focal length of a lens is the point from a certain point in the optical system to one of the principle foci (for practical purposes the image plane). In a thin lens (where the thickness is negligible compared to the focal length) this is from the centre of the lens. In a multi-element camera lens it is from the rear nodal point (which can be outside the physical structure of the lens, woooo, spooky).

Confused? You bet, and that is a gross oversimplification.

You can have a look at Wikipedia and read up on all of this if you like. But you don’t really need to know it all. Continue Reading “Focal Length, Depth of Field, and Field of View”