Buy smart, Buy once
Make sure that you buy a circular polariser rather than a linear polariser. Both are round in shape but block polarised light in different ways – for digital photography, only a circular polariser will work. Circular polarising filters can be expensive, costing anything from £ 20 up to £ 250 and above, depending on the size and brand that you go for. As you’re likely to have several lenses, possibly with different filter threads, it’s going to be expensive if you buy a filter size for each lens. Instead, buy a filter to match your largest filter thread and then pick up more cost- effective step- up ring adaptors so you can fit the filter to the smaller lens threads.