CP for 50mm f/1.8

What size CP will I need for my 50 mm f/1.8? Also, if im to get the 70-300mm f/4, should I get a larger CP and then get step down rings for the 50?

Thanks!

50 f/1.8 has a 58mm thread so does the EF 75-300 f/3.5-4.6 USM III BUT the 70-200 f/4 has a 67mm filter thread. You could by a nice (expensive) B+W 67mm CP and get a 67mm to 58mm step down (or is it step up, I cant remember) from ebay. The only caveat is that you WONT be able to use a hood (if you have one) on your 50 1.8 with your 67mm filter.

50 f/1.8 has 52mm thread (the 50 f/1.4 is 58mm thread)

Oh ok...I have the 50 1.4 and a couple of other 58mm filter thread lens. I guess OP needs 67 to 52 stepping ring then.

thanks a ton!

You may be able to use the 70-200 f/4L's hood with the 67mm filter and step ring in the 50mm f/1.8 because the L's hood is designed for 70mm (focal length), and the nifty's effective focal length is 80mm... Am I wrong?

Its not an L lens, it's the 70-300 f/4 non-IS

Oh wow, I've messed up. It's the 75-300, not the 70-300. Therefore, what size does this lens use for CP?

75-300 takes 58 mm.