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Canon EOS Crop Sensor for HD
APS-C sensor cameras including the 80D, 70D, 7D Mk. II, 7D, EOS M and Rebel models for HD video recording.


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Old December 4th, 2009, 10:48 AM   #1
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problem with aperture value when i zoom ?

Hi! In video mode When I zoom with my 15-85mm the aperture value changes automatically (exposition ?) ... how to avoid it or disable this function !
Because of that i can' t zoom and make video without light changing !

Thanks !
Daniel
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Old December 4th, 2009, 10:56 AM   #2
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Daniel,

The 15-85mm is a variable aperture lens. As you zoom it HAS to adjust the aperture accordingly due to the design of the lens. The way around this is to purchase a fixed aperture lens (it will say something like "f2.8" rather than "f3.5-5.6").
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Old December 4th, 2009, 11:04 AM   #3
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Dan - the aperture value only changes automatically if you're shooting at full wide and max aperture. Try it the other way around - shoot at full tele and max aperture - then zoom to full wide - you'll see that the aperture doesn't change.

Craig's right, you need to buy a fixed aperture zoom lens (usually a lot dearer than the vari-aperture lens you've got)

tom.
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Old December 4th, 2009, 12:35 PM   #4
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Weeell... You don't NEED to...
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Old December 4th, 2009, 01:02 PM   #5
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he needs to if he wants to (quote) 'make video without light changing'.
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Old December 4th, 2009, 01:49 PM   #6
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I understand now !
I must to purchase a fixed aperture lens : maybe the 50mm f1.4 or 1.8 !
Thanks a lot for all of yours !

Daniel
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Old December 4th, 2009, 01:51 PM   #7
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Well you'll find it difficult to find a fixed aperture lens, but I know what you mean.

No - you want a constant maximum aperture zoom. Yours is probably 15 - 85 mm f/2.8 to f/5.6, something like that. What you want (what we all want) is a 15 - 85 mm lens that has a maximum aperture of f/2.8 throughout the zoom range.

tom.
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