I have this lens, a Canon 50mm f/1.8 STM:

enter image description here

I would like to purchase a polarizing filter for the lens but I can't seem to find one. A quick search on Amazon, for example, yields plenty of 49mm and 52mm filters but none for a 50mm lens.

Am I looking for the wrong number? Am I looking in the wrong places?


1 Answer 1


Yes, you are looking at the wrong number. Since the filter screws to the front of the lens, the only number that matters is the diameter of the filter thread, not the focal length of the lens.

Look at the front end of the lens. Around the glass is a ring with text on it. One number will have a symbol a little like Ø next to it, probably 52. This is the filter size.

  • 2
    \$\begingroup\$ The lens has ϕ49mm printed on it. Thanks for the clarification! \$\endgroup\$ Commented Sep 12, 2016 at 20:32

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