Can someone help me decipher the specs of a camera lens.

Purely for example, I see a lens being advertised as:

AF Nikkor 24-50mm 1:3.3-4.5 Wide Angle Zoom

What is AF? What exactly does 24-50mm refer to? What is 1:3.3-4.5 telling me?

In general, are there quick observations you can make from seeing specs like these, for example, saying "ah yes, 24-50mm is good for indoor weddings" etc.?

  • \$\begingroup\$ As for "what focal length is good for x situation" it really depends. We have examples for portrait photography(photo.stackexchange.com/questions/916/…), but generalizing a focal length into exactly what it is good for simply does not make sense. It makes more sense to ask what focal lengths work for a particular type of photography then the other way around. It would be like asking what brush is good for a certain type of painting, of course the answer is, it depends. \$\endgroup\$
    – dpollitt
    Jul 24, 2013 at 3:26

1 Answer 1




Note that with a Nikon lens, "AF" alone, not followed by other letters, means that it's the older type of autofocus which requires an autofocus motor in the body of the camera. It's an older, slower, noisier type of autofocus than a modern "silent wave" autofocus, which would be designated by "AF-s". It also means it's not compatible with all camera bodies, particularly smaller/prosumer ones. Note also that Nikon lenses designated "AF" but not "G" have an aperture ring, so you control the aperture on the lens itself.

(All this and more can be referenced here).


Brand name of the lens. Nikon still produces lenses under the "Nikkor" brand.


Focal length range of the lens, indicating that this is a zoom lens.


Maximum aperture at the wide end, and telephoto end, of the lens, respectively.

At the wide end, the maximum aperture is f/3.3. At the telephoto end, the maximum aperture is f/4.5.

The aperture relates to the effective diameter of the area of light allowed to pass through as a ratio compared to the focal length. f/2 would mean the diameter is one half that of the focal length. f/4.5 means the diameter is the focal length divided by 4.5, which means less light can pass through. Remember that it's a diameter of a round opening so halving the diameter actually divides the light coming in by 4.

In simple terms it just means how much light it lets in and therefore how well it will perform in low light situations given all else is equal.

Wide Angle

Designates that the wide end is wide enough to be called "wide angle". The is redundant since it gives the focal length range anyway.


We already knew it was a zoom because it gave the focal length range.


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