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Filter size question

James3shin

James3shin

Diamond Member
I was looking at filters and noticed that lens size does not match up with filter size. For instance, I want to get a filter [or hood, still debating] for a Canon 50mm F1.8 and B&H suggested a 52mm filter. Are these filters threaded to screw onto a lens or are they applied like stickers?
 
50mm is the focal length of the lens. The 52mm refers to the front diameter of the lens thread. Most filters are threaded onto the front of a lens, so in your case, you need a 52mm filter for the 52mm front thread diameter on your 50mm f/1.8.

Lenses with faster f/stops tend to have larger front openings, since the f/stop is the ratio of the lens's focal length divided by its maximum aperture opening. Therefore, a 200mm f/2.8 needs to have a maximum diameter opening of about 71.5mm, and as such uses a large 77mm filter thread. It is often possible to use larger filters with a step up ring on your 50mm lens; usually, using a 77mm filter on a lens with a 52mm filter thread won't cause any vignetting.
 
Originally posted by: 996GT2
50mm is the focal length of the lens. The 52mm refers to the front diameter of the lens thread. Most filters are threaded onto the front of a lens, so in your case, you need a 52mm filter for the 52mm front thread diameter on your 50mm f/1.8.

Lenses with faster f/stops tend to have larger front openings, since the f/stop is the ratio of the lens's focal length divided by its maximum aperture opening. Therefore, a 200mm f/2.8 needs to have a maximum diameter opening of about 71.5mm, and as such uses a large 77mm filter thread. It is often possible to use larger filters with a step up ring on your 50mm lens; usually, using a 77mm filter on a lens with a 52mm filter thread won't cause any vignetting.
Click to expand...

a good 77 mm filter will cost about as much as a 50 f/1.8, so i wouldn't go that route myself
 
Originally posted by: ElFenix
Originally posted by: 996GT2
50mm is the focal length of the lens. The 52mm refers to the front diameter of the lens thread. Most filters are threaded onto the front of a lens, so in your case, you need a 52mm filter for the 52mm front thread diameter on your 50mm f/1.8.

Lenses with faster f/stops tend to have larger front openings, since the f/stop is the ratio of the lens's focal length divided by its maximum aperture opening. Therefore, a 200mm f/2.8 needs to have a maximum diameter opening of about 71.5mm, and as such uses a large 77mm filter thread. It is often possible to use larger filters with a step up ring on your 50mm lens; usually, using a 77mm filter on a lens with a 52mm filter thread won't cause any vignetting.
Click to expand...

a good 77 mm filter will cost about as much as a 50 f/1.8, so i wouldn't go that route myself
Click to expand...

I know, but I'm just saying, in case he ever decides to buy a lens using 77mm filters, they are still usable on his 50mm f/1.8 II using a step up ring.
 
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