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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 05 Oct 2011 (Wednesday) 18:55
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Can you explain this to me

 
Litespeed
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Oct 05, 2011 18:55 |  #1

I have just ordered a Canon EF-S10-22mm lens. It says that the aperature is F3.5-4.5. Yet you can set your aperature to F22 if you want.

What am I missing here?


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Oct 05, 2011 18:57 |  #2

Maximum aperture varies from 3.5 (when at 10mm) to 4.5 (when at 22mm). Similar to your 18-55 and 55-250.


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joeseph
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Oct 05, 2011 18:57 |  #3

the maximum apeture is different at either end of the zoom range...


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OneJZsupra
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Oct 05, 2011 19:03 |  #4

^^^
When it is at its widest your Max aperture is 3.5 but as you zoom the lens in to 22mm it stops down to 4.5, which is the Max aperture for that lens at 22mm. The min. aperture stated is f22 which is the smallest the aperture can get (For max depth of field but little light enters, which you would only need for landscapes that you're trying to drag the shutter for or other creative things like that.


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jlw470
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Oct 05, 2011 19:03 |  #5

f22 is the smallest it will get




  
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Litespeed
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Oct 05, 2011 19:32 |  #6

Ok, thanks for the explanation, I think I kind of understand it. Guess it doesn't really matter as long as it does what I want to do, I've never been good at technical stuff.


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huntersdad
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Oct 05, 2011 19:35 |  #7

I may be wrong, but I think you're asking if the aperture is 3.5-4.5, how can you stop it down to f/22?

F/22 is the smallest you can stop the lens down, meaning change the size of the opening for light to come through. This increase DOF at the expense of a longer SS assuming ISO remains the same.


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Stump
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Oct 05, 2011 19:42 |  #8

I think, Litespeed thinks that "3.5-4.5" means that's the range of aperture available. But that would be 3.5-22 at 10mm.

When the lens are listed as 3.5-4.5, that's only the maximum aperture available. The 3.5 is the biggest aperture available at the widest part of the lens, the next number refers to the biggest aperture available at full zoom. In this case f4 @ 22mm.


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Bananapie
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Oct 05, 2011 19:46 |  #9

^ Good information in this thread for you.

Though to make things VERY clear: Lens names list their WIDEST/biggest/fastest​/maximum aperture.

A "constant" aperture lens, like the 24-70 f2.8L, is somewhat of a misnomer, as you can select a range of apertures. The reason it is labeled constant is because no matter what focal length you choose, you can always set it at its widest aperture of f/2.8.




  
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Litespeed
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Oct 05, 2011 20:05 |  #10

I think what I can't get my head around is why they list it at F3.5 - F4.5. To me, I'm thinking it won't have a small aperature opening, just wide open. If it will actually go down to a small aperature opening why are they trying to confuse me?


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ChuckingFluff
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Oct 05, 2011 20:10 |  #11

This should sort out a lot of your confusion and don't forget to take some pictures and share them.

http://mansurovs.com …s-aperture-in-photography (external link)




  
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artemisn
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Oct 05, 2011 20:10 |  #12

If it was a constant f/3.5 lens, it would require much more glass. The layout of the elements inside the lens change when you zoom, and it takes more glass to retain enough light to keep it at f/3.5 at both ends of the zoom.

A good example of this is the weight difference between the 70-200mm f/4 and f/2.8. To get more light, you need more (and bigger, if I'm correct) lens elements, and those can seriously affect the weight and size.

A more extreme example would be comparing the sheer size of the 85mm f/1.8 and f/1.2 : http://780x378-1.ikiwq.com/IUOG9BYPH1​nZkaMILlm2Vd.jpg (external link)


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cacawcacaw
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Oct 05, 2011 20:56 |  #13

Litespeed wrote in post #13210855 (external link)
I think what I can't get my head around is why they list it at F3.5 - F4.5.


When using the lens at its widest angle (10mm), the aperture can be set between f/3.5 (wide open) and f/22 (the opening closed down as much as possible).

When zoomed in (22mm), the aperture range changes and the aperture can be set anywhere from f/4.5 to f/29. (The range changes because the f-stop is the ratio of the focal length to the size of the aperture opening.)

All lenses advertise the maximum aperture (lower f stop) because lenses that have larger apertures require larger glass elements which are desirable but expensive. The larger the maximum aperture, the faster the lens will meter and focus. And, the larger the aperture, the more light is admitted and more the Depth of Field is narrowed, making expensive large-aperture lenses superior when used in low light or when trying to isolate the subject (having everything out of focus except for the subject).

Wide-angle lenses are typically used for landscape and architectural shots where you'd want most of the image in focus. Because wide-angle lenses are not typically used with the aperture wide open (which isolates the subject from the foreground and background), there is not much demand for wide-angle lenses with very large apertures. Nonetheless, all lens specifications include the maximum aperture, which in this case ranges from f/3.5 to f/4.5.


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xarqi
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Oct 06, 2011 02:53 |  #14

Litespeed wrote in post #13210855 (external link)
I think what I can't get my head around is why they list it at F3.5 - F4.5. To me, I'm thinking it won't have a small aperature opening, just wide open. If it will actually go down to a small aperature opening why are they trying to confuse me?

Nobody is trying to confuse you, you have just not understood what you are being told.

The f/3.5-f/4.5 is not the range of available apertures, as you have assumed, it is the range of MAXIMUM apertures available.




  
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Sirrith
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Oct 06, 2011 05:20 |  #15

Think of it this way. Your 100mm macro is a prime, so it only has one focal length. It says f2.8, does this mean you can only use it at f2.8? No. Your 10-22 is a zoom lens. That means it has more than one focal length. Not all those focal lengths can open at f3.5. If you think of it as a collection of prime lenses, from 10-22mm, all rolled into one, some of those primes are f3.5, some are f4, some f4.5. They, like the 100mm, can be stopped down. Canon is merely telling you that the slowest of these "primes" is f4.5, and the fastest is f3.5.


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