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Old 02-05-2013, 09:50 AM
cfranks (Charles)
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Canon EF 70 - 200 f2.8L IS USM Zoom lens

I've fitted this lens to my QSI683ws and ask is there any way to reduce the aperture from the (apparently) fixed 2.8 to, say, 4.5 or so? I think I read somewhere that mounting it on a Canon camera, taking a long exposure at f 4.5 and removing the lens while the exposure is underway will leave the lens set at 4.5! Seems very dodgy to me so I thought I would ask the experts here.

Charles
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Old 03-05-2013, 05:53 AM
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troypiggo (Troy)
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Not dodgy, just inconvenient.

Only other way I can think of is to make an external aperture. Ie a circular disk over front of lens. Some use cardboard for simplicity. Other DIY lens cap mods or use filter step rings.
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Old 03-05-2013, 08:38 AM
cfranks (Charles)
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Thanks Troy, I was going to try that. I bought a 'nested set' of filter reducer rings to try when the clouds go away. I know nothing about the construction of these lenses and didn't know if there is a variable aperture built in that the camera controls electronically. Hence the naff question!

Charles
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Old 03-05-2013, 12:41 PM
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Octane (Humayun)
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Don't remove the lens during an exposure.

Instead, stop down the lens to whatever aperture you desire, press the depth-of-field preview button on the side of the body, and, then remove the lens while the button is depressed.

H
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Old 03-05-2013, 03:15 PM
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troypiggo (Troy)
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D'oh. What H just wrote is what I had in my brain that you had written in the OP. Completely misread your method. He's right. For once.
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Old 03-05-2013, 06:11 PM
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Octane (Humayun)
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lol, cheeky.

H
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Old 03-05-2013, 07:00 PM
cfranks (Charles)
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Quote:
Originally Posted by Octane View Post
Don't remove the lens during an exposure.

Instead, stop down the lens to whatever aperture you desire, press the depth-of-field preview button on the side of the body, and, then remove the lens while the button is depressed.

H
Thanks Octane, that was what I had read before!! I don't feel too much of a dummy now, just a bit forgetful!

Charles
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