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Old 28th of December 2006 (Thu)   #1
troyer16
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Default When a lens list the appeture what does that mean?

sorry for the newbie question, but lets say like this:
Sigma Zoom Normal-Telephoto 55-200mm f/4-5.6 DC Autofocus Lens for Canon Digital EOS



why does it list f/4-5.6?

Thanks
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Old 28th of December 2006 (Thu)   #2
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Default Re: When a lens list the appeture what does that mean?

Quote:
Originally Posted by troyer16 View Post
sorry for the newbie question, but lets say like this:
Sigma Zoom Normal-Telephoto 55-200mm f/4-5.6 DC Autofocus Lens for Canon Digital EOS



why does it list f/4-5.6?

Thanks
f4 is as wide an aperature as it will go and as you zoom out to the 200mm mark it will have an aperature of f5.6

if that doesnt make sense im sure someone else can explain it a little bit better than me lol
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Old 28th of December 2006 (Thu)   #3
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Default Re: When a lens list the appeture what does that mean?

That also means that lens won't be very good in low light. To get better pictures in situations with lower light, a lens with a maximum aperture of f/2.8 or wider (i.e. lower number) is better.
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Old 28th of December 2006 (Thu)   #4
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Default Re: When a lens list the appeture what does that mean?

Quote:
Originally Posted by troyer16 View Post
sorry for the newbie question, but lets say like this:
Sigma Zoom Normal-Telephoto 55-200mm f/4-5.6 DC Autofocus Lens for Canon Digital EOS



why does it list f/4-5.6?

Thanks

At 55mm its max aperture is f/4, at 200mm its max aperture is f/5.6.

So starting from 55mm f/4, when zooming the max aperture will become smaller (bigger f value) based on corresponding focal length...until it reaches 200mm f/5.6.

When you see a lens like EF 70-200 F/2.8 that means the max aperture at any given focal length between 70-200 is 2.8...so this is constant 2.8.
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Old 28th of December 2006 (Thu)   #5
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Default Re: When a lens list the appeture what does that mean?

oh ok thanks! i kinda get it, so if i zoomed out to the 200mm mark, it would be an f of 5.6 but that doesnt mean it has to be, i can shoot at 200mm with an f of 11 if i want right?
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Old 28th of December 2006 (Thu)   #6
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Default Re: When a lens list the appeture what does that mean?

Quote:
Originally Posted by troyer16 View Post
oh ok thanks! i kinda get it, so if i zoomed out to the 200mm mark, it would be an f of 5.6 but that doesnt mean it has to be, i can shoot at 200mm with an f of 11 if i want right?
Yes...the f/5.6 is just the max aperture...so you can go f/11...
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Old 28th of December 2006 (Thu)   #7
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Default Re: When a lens list the appeture what does that mean?

If the max aperture of the lens is constant throughout it's zoom range, then you will only see one aperture listed.

Example: 70-200 f4.0

That's typical of the top zoom lenses.

Other lenses have varying max apertures. The less you zoom it out (like 55mm), the wider the aperture.

Example: 55-200 f4.0 - 5.6

So; at 55mm, the max is f4.0. At 200mm, the max is f5.6. At any mm in between, the max varies proportionally. So at 100mm it may be f4.5.

EDIT: Wow - a lot of people jumped on this one right away! Sorry about the repeat, guess I'm the slowest typer.
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Old 28th of December 2006 (Thu)   #8
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Default Re: When a lens list the appeture what does that mean?

thanks all, one more quick question
again lets say 200mm with the same lens, i could NOT shoot at f 5.0 though right, has to be at least 5.6?
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Old 28th of December 2006 (Thu)   #9
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Default Re: When a lens list the appeture what does that mean?

Quote:
Originally Posted by troyer16 View Post
thanks all, one more quick question
again lets say 200mm with the same lens, i could NOT shoot at f 5.0 though right, has to be at least 5.6?
The max you could shoot at 200mm would indeed be at f/5.6.

Bing!
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Old 28th of December 2006 (Thu)   #10
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Default Re: When a lens list the appeture what does that mean?

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Originally Posted by nicksan View Post
The max you could shoot at 200mm would indeed be at f/5.6.

Bing!
thanks makes perfect sense now!
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