Email Q&A: a question about lenses & those f/#s
I just got another very good question about lenses.
Here’s the email:
Hey Carey!
… I have a quick question about the more costly lenses. When you get a higher quality lens (like your favorite 70-200mm), can you retain the 2.8 f-stop when you zoom? I have a cheap-o 70-200mm and when I zoom, my aperture narrows. Other than the amazing glass in the more costly lenses, do I get to zoom to 200mm and still shoot wide open at f 2.8?
Thanks!
Carol Anne
Here’s my answer:
Hi Carol Anne!
Great question! When you buy a lens, it will say something like f/2.8 (like my favorite 70-200mm) or f/4-5.6 (like THIS one).
When a lens has ONE number after the “f/” that means you can use that setting no matter how wide or tight you zoom the lens.
If you see a lens that says something like “f/3.5-5.6″ with two numbers, that means you can use the lowest number (for faster shutter speeds, more light, and better background blur) only when you’re NOT ZOOMING the lens in tight. Once you start zooming in, you can’t use that low number any more, and the lens will switch to a higher f/#. When you zoom as much as possible, the lowest number you’ll be able to use will be that 2nd number on the lens.
Why?? Cuz it’s difficult to make a zoom lens that can maintain a wide aperture no matter how much or how little you zoom. Better glass is needed. Better mechanics and optics inside are needed. They’re harder to make, and that means $$$, so those lenses are more expensive.
Rock on!
~Carey
I will definitely “rock on”! And you keep rockin’! Cause you do. Rock, that is.
Thanks!
Testing a new comment thingee….
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I am interested in buying the 80-200 f2.8 Nikon lens used for $600.00 is this lens worth that money used? thanks
Hi Tammy! I love my canon 70-200 f/2.8. Having a constant 2.8 aperture available, regardless of your zoom, is a sign of a high-quality lens, and $600 is a good price. I say go for it!