Zoom Lens Question

[JamesV]

Hello everyone,
Well I have stepped up and purchased the Canon XTi w/ 18-55 lens kit and the 50 1.8 lens. I now have a question about zoom lens, as this is the next lens that I want to purchase.
I want to know is there a formula or simple way to figure out a way to know how close to an object a 200mm or 300mm lens will get you. I would like to know because I was looking at the 70-200 or the 70-300 and use it for landscape and sports events.

Thanks in Advance,
James

[mn shutterbug]

With 35mm cameras, about 50mm was considered a normal lens, not telescopic and not wide angle. I believe your camera has a zoom factor of 1.6. This means that your 50mm lens is basically an 80mm telescopic lens. A 200mm will get you out to 320mm and a 300mm will reach 480mm. If you divide the 320mm by 50, you end up with the equivalent of 6.4 power and the 480mm divided by 50 gives you 9.6 power. In other words, the 200mm lens will pull things in 6.4X closer and the 300mm, 9.6x closer. You could compare this to binoculars. A binocular that is 7 X 50 enlarges the subject 7 times, whereas these 2 lenses enlarge the subject 6.4 times and 9.6 times.

I hope my explanation helps. I guess you could maybe figure it this way. If a subject is 100feet away and you are using the 300mm lens (480mm zoom factor), which is equivalent to 9.6X, the subject will appear at a little over 10 feet, due to everything being magnified close to 10 times.

[JamesV]

Mike,
Thanks for the answer, that is exactly what I was looking for.

James