What do the Numbers on Lenses Mean?

I have a Nikon D3100

i was looking at this lens to buy:

Nikon Nikkor 55-200mm Zoom Lens VR Image Stabilization, f/4-5.6G, IF-ED, AF-S,

what do the " f/4-5.6G" mean? Is the higher/lower the better or what?

what about this lens?

Nikon 70-300mm f/4-5.6G AF Nikkor SLR Camera Lens

It's the maximum aperture that the lens is capable of (ie how much light it can let in). Because it's a zoom lens, there are 2 numbers.

f4 is the maximum aperture it can achieve at 55mm focal length, f5.6 is the maximum aperture it can achieve at 200mm focal length.

Ditto the 70-300mm - you'll have f4 as your max at 70mm and f5.6 as your max at 300mm.

These are not particularly 'fast' lenses - a fast lens is one that will allow a wider aperture (f2.8 or so) throughout the range, but they are reasonable consumer lenses.

Where they will let you down is in poor light conditions. For example, if you are shooting with a 70-300mm lens at the 300mm end in low light, the most you can open up the aperture is f5.6 - that's not very much. In order to get a good exposure, you'll probably have to raise the ISO which will decrease image quality.

It's the range of maximum apertures the lens is capable of.

f/4 to f/5.6

F/4-f5.6 means a lens with a variable aperture. As stated above, as you move through the zoom range, the maximum aperture will vary from f/4 at the wide angle end to f/5.6 at the telephoto end.

This is the mark of a consumer lens.Pro lenses will have a fixed aperture along the entire zoom range, so they will only have one f marking (i.e.f/2.8), which means the same maximum aperture along the entire zoom range. It simply costs more to create a constant aperture zoom lens, which is one reason pro lenses are more expensive.

That doesn't mean consumer lenses are bad - they just don't have quite the low-light capability that pro lenses will have.

"G" means that there's no aperture adjustment ring on the lens. This is not an issue for any modern DSLR, unless you have a specific purpose such as using a reversing ring for macro use - at which point, a lens-adjustable aperture is a nice thing to have.

Also, you are comparing an AF and AF-S lens.

Lenses marked "AF" have no internal focus motor, so they will not autofocus on your D3100 as your camera lacks a focus motor. A D90 and above is required to autofocus these lenses.

"AF-S" lenses do have internal focus motors and will autofocus on your D3100.

55-200mm is just how much zoom you have in the lens

50mm is usually what your eyes see without moving your head around.

If you set you lens at 80mm that is already a zoom, it brings the image closer to you.

f/4-4.6 those are the most important numbers that define the quality of the lens.

Again the first mm numbers are just telling you what zoom you are having.
Of course there are fixed lenses that would have just one mm number lets say 20mm and tham means that is is so wide that using this lens the camera will see much more then what your eyes see without turnig you head around, remember 50mm is what human vision is.

f number is the most important THE LOWEST THE F IS THE BETER THE LENS

That tells you how much light will the less allow to com inside the camera.
What is meant is that if you have f/2 there will be much more light and of course detail and color and everything then f/4.

Some great fixed lenses would be about 50mm f/2.3

Since your lens is zoom the 4 is aquivalent to 55mm and when you set your lens to 200mm then you have f5.6

Hope this helps

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