If your anything like me you probaly have lenses of various diameters. Some of the more common ones for Canon Lenses are 52mm, 58mm, and 72mm. Well, I spent a fair chunk of money to get a very high quality Circular polarizer in the Tiffen unit. But a couple of my favorite lenses are my Nikon 135mm, and Canon 50mm 1.8 Mk2. Both of these lenses are actually smaller than the 58mm polarizer. As well they are actually smaller than all of my filters. So you might think I had to buy another set of filters for these lenses. We’ll, your wrong!
You can actually use the 58mm filters you already purchased with these lenses. You can simple go into your local camera shop and ask for a 52mm to 58 mm step up ring. One end fits the 52 mm size of your lens, and as the name implies the other end allows 58mm filters to be screwed in. This is a great thing to have, especially for things like ND Grad filters which you may not use everyday. You can now simply by one set of high quality filters and use them on all your different lenses.