 BetterPhoto Member |
Zoom Lens I am interested in buying a zoom lens for my Minolta 7000 Maxxum Camera. (I have read your section on purchasing a lens) I currently have a 28-85 AF Lens. I intend to use the zoom lens for outdoor photography - nature, landscapes, and sports action. I believe a 100 to 300 or a 100 to 400mm zoom would be great. However, I am confused as to the numbers (F 4.5-5.6, F 4.5-6.7, f-stops?) that are offered with the lens. How do I determine which lens to get with which numbers/f-stops? Thank you for your time.
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John A. Lind |
Dave, Yes, those numbers are aperture f-numbers. They represent the widest lens aperture opening possible on the lens, often called the lens speed. The lower the f-number, the wider the aperture, and the faster the lens. The higher the f-number, the narrower the aperture, and the slower the lens. The reason for a range, such as f/4.5~5.6 is that the widest possible aperture changes with the focal length. Assuming this aperture range is associated with the 100-300mm zoom, if you stopped the lens aperture completely open, it would be f/4.5 at 100mm and f/5.6 at 300mm. A focal length in between would have an aperture in between these. If you stop the lens down from the widest aperture setting, the aperture should remain constant. This means the changing aperture as you zoom should only happen with the widest aperture setting. -- John
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