- Make sure your photographer can use one. Most compact cameras can’t take them because polarising filters screw in to a shallow thread at the very front of the lens, and compacts don’t have this. On the other hand, almost all interchangeable lenses – the sort used in DSLRs – do.
- Make sure you get the right size. Look inside the lens cap and you will probably see a marking giving the diameter of the lens (in millimetres). If not, measure it. Remember, different lenses have different diameters so, even if your photographer already has a polarizing filter, he/she may appreciate another for a different lens.
- If your photographer owns a digital camera make sure you get a circular polarizing filter. No, this does no refer to the shape – they are all circular – but the type. (The other type is ‘linear’). The one you want should be marked ‘Circular Polariser’, or bear the abbreviation Cir, PL Cir, or CPL. If in doubt, ask an assistant.
using a polarizing filter to make the water stand out against the sky.