Canon EF 28-135mm IS lens, is it f3.5-5.6, or f3.5-22 as shown on camera? at DVinfo.net

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Old March 7th, 2010, 07:34 PM   #1
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Canon EF 28-135mm IS lens, is it f3.5-5.6, or f3.5-22 as shown on camera?

Canon 7D, stock lens Canon EF 28-135mm IS

All the printed matter and web research says this lens is f3.5-5.6.

But in action, the camera shows it going up to f22.

So which is it? It does not seem possible for the camera to go up to f22 on a lens that specs out at 5.6
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Old March 7th, 2010, 07:40 PM   #2
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Keith,

All lenses will be able to be stopped down below their widest settings. I have that lens and can confirm that it behaves that way. 3.5-5.6 is the WIDEST you can open the aperture based on how zoomed in you are. At 28mm, you can open to f3.5. At 135, you are limited to f5.6. I don't remember exactly at what points the aperture ramps (and it does ramp in jumps, it is not a smooth process). Does that make sense?
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Old March 8th, 2010, 09:11 AM   #3
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Thats what I thought. When the lens is on the camera, the LCD aperture reading goes all the way to f22. Yet the lens specs say f5.6. Weird.
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Old March 8th, 2010, 09:17 AM   #4
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Okay, now I get it. Thank you. I'm an old film guy used to cine prime lens, didn't use zoom lense very much, so I didn't even realize the f stop would change with zoom position.

thanks,
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Old March 8th, 2010, 09:28 AM   #5
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Keith, the f3.5-5.6 specification refers to the lower f value. The lens has a variable aperture and the lens will change its lowest f value between those numbers when zooming. You can put it to f3.5 and you will see it will change itself to 5.6 when you zoom.
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Old March 9th, 2010, 09:44 PM   #6
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Keith, there are fixed aperture zoom lenses, but they cost more.
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