What do the numbers above on Nikon prime lenses mean? 50mm 1.8G When buying a uv head, should you look at 50mm or that one?

1. The number in mm refers to the focal length of the lens. If this number is an interval value (such as 16-85mm), it means that the lens is a zoom lens and its focal length can vary from 16-85mm. ; If it is just a numerical value (such as 50mm), it means that the focal length of this lens is fixed at 50mm, that is, a "fixed focus lens".

2. 1.8 is the non-standard abbreviation of "f/1.8". The number indicates the maximum aperture of the lens. 1.8 means the maximum aperture is f/1.8. If the number is an interval value (such as f/3.5-5.6), it means that the maximum aperture of the wide-angle end of the lens at the minimum focal length is f/3.5, and the maximum aperture at the telephoto end at the maximum focal length is f/5.6; fixed focus The lens will not have an aperture marked with an interval value, and some zoom lenses will not be marked with an interval value, which means that the maximum aperture of the lens at the wide-angle end and the telephoto end is the same. This kind of zoom lens is called a "constant aperture" lens. .

3. Each lens will be marked with a lens diameter. For example, the φ58mm marked on the lens you mentioned is the lens diameter. You can buy UV filters or polarizers according to this size. They are universal for all brands. of.