Originally Posted by Dieben
Nobody has mentioned lens filters!
So what do you need to know?
Filters. Well, there are/were thousands of different filters. Kodak once made vast numbers of gelatin filters. Specialty filters, color filters, contrast filters and the like.
Lots of filter manufactures at one time. For example Ednalite. Tiffen still makes filters, but their catalog lacks many of the best filters.
I use series size filters because I can use them on different cameras and all I need is an adapter and step-up/step-down rings.
Some filters are costly and some are cheap and some are poorly made and some are well made. For example, I favor old school Kodak rings and adapters. They were machined from stainless steel rather than aluminum.
If you shoot color, you need different filters than you require for contrast control in black and white.