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Have you ever looked at your lens and wondered just what the heck all of those numbers meant? A lot of people make it out to be harder than it really is, but the numbers are all important numbers that stand for something that can help you identify the lens or accessories for that lens.

So What Does It All Mean?
The following is a picture of the standard kit lens that comes with most consumer Canon digital SLRs.

Canon Zoom Lens: Lens is made by Canon. "Zoom" means that the lens is not fixed at one focal length. Rather, it is "zoomable" in that you are able to change the focal length of the lens.

EF-S: The type of mount the lens will fit on. Canon's current mounts are EF and EF-S. EF lenses can fit on EF-S mounts, but EF-S lenses cannot fit on EF only mounts.

18-55mm: This is the actual focal length of the lens. To get the 35mm equivalent (on 1.6x crop camera bodies) multiply both numbers by 1.6; that makes this lens a 29-88mm standard lens.

1:3.5-5.6: This number trips a lot of people up. This is actually the maximum aperture of the lens. 1:3.5 means f/3.5 at the wide angle end (18mm) and 5.6 means f/5.6 at the telephoto end (55mm).

Φ58mm: A lot of people are confused by this number too. This merely tells you what size filters will fit your lens. Therefore when you go to the camera store, you will know to buy a 58mm UV filter and not a 77mm UV filter.

Summary: 18-55mm 1:3.5-5.6 Φ58mm = Focal length (zoom lens) of 18-55mm with a maximum aperture of f/3.5-f5.6 and accepts 58mm filters.

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