 Jenna M. Anderson |
Filter Factors: What About Size? Hi. I know that there has been a ton a questions asked about which filters people should buy. However, my question is, after you know with one you want, how can you tell which size you need? I want one that will fit a 75-300mm lens. Also, is it necessary to buy a step-up or step- down attachment? Thanks for any advice.
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Jon Close |
Screw-on filters are sized by the diameter of its ring threads. The lens should have its filter thread diameter marked on the front with the Ø symbol, eg., "Ø55" for 55mm filter threads. Step-up/down rings match filters made for one thread size to a lens with another. A step-up ring is common and allows use of a larger filter on a smaller diameter lens. For example, a 62mm filter can be mounted on a lens with 58mm threads by using a 58/62 step up ring - 58mm male threads on one side of the step-up ring screws onto the lens, and on the other side are 62mm female threads onto which the filter is screwed. Using step-up rings one can buy a single set of filters in the largest size they need instead of buying the same filter several times for each sized lens. Step-down rings are similar, but are used for attaching filters with smaller diameter threads than the lens. This is less common and is practical in only specialized cases because filters of smaller diameter than the lens will create vignetting - blocking light to the outer portion of the film frame.
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