zoom lens important?

Question:

Is the built in aperture ring on some telephoto/zoom lens important?

i looking out for a telephoto lens....need to know if the aperture ring provided on some lens, a prefered choice over the one's whithout it and why....?what is the best telephoto lens under $250 for my canon eos 400d...

Best Answer - Chosen by Asker: For the EOS series, the Aperture ring is a plus but almost unnecessary. Honestly, if you know or plan on learning what the Aperture actually does, you'll find the Aperture Ring invaluable. But you'll still have control using your spin wheel in AP or Manual modes. Also, unless you have a camera with Aperture preview, you'll be guessing so again the Ring becomes only an expert feature.

In case you're not sure what that means, aperture controls how much light a lens lets in at one time. The numbers are a ratio (example1:2.8 or 1:3.5, etc) but the "1 to" (1:) is normally dropped and just the last number are normally represented. Ideally, a lens would let in 1:1 but that's incredibly hard because of the mechanics. You'll notice when selecting lenses, a lower AP number is more expensive. Last thing about aperture is that it also controls your "depth of field"; which in basic terms is "how much is in focus at once". The best example would be you take a picture of a flower. If you used an AP of 2.8 only the flower would be in focus and the background is just a color blur. In contrast, if you used an AP of 18, you'll see the background pretty clearly. With a Ring, you can control the Aperture faster but isn't necessary for stationary subjects.

As for lens selection, it's hard to say which lens the best; your style of photography dictates which lens is the best for you. For instance, a sports photographer will select a (high #)mm lens with the widest Aperture (closest to 1) their budget affords them. But a paparazzi/candid photographer will look into the range of focal lengths (the mm range). For general purposes, I'd recommend something like a 28-135mm lens (or something close to those numbers). This will allow a slight wide angle but you'll have the option of zooming in. Also, unless you're picky, you don't need to step up to a Canon lens. You may find Sigma and Tokina great substitutes for the price. Again, ultimately this will be decided based on your needs.