Aperture Override for IXUS 85/SD770 - Feature Requests - CHDK Forum
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Aperture Override for IXUS 85/SD770

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Offline maor1993

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Aperture Override for IXUS 85/SD770
« on: 20 / June / 2011, 11:16:09 »
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Hello, I recently got CHDK for my Ixus 85, It's working great but I can't understand there isn't aperture override in the menu, even though I've seen my camera going to lower apertures than f/4.9

I hope you can help me.

Thanks in advance,
Maor.
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Offline fe50

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Re: Aperture Override for IXUS 85/SD770
« Reply #1 on: 20 / June / 2011, 11:25:49 »
Hello & welcome, maor1993 !

Quote from: maor1993 on 20 / June / 2011, 11:16:09
I can't understand there isn't aperture override in the menu, even though I've seen my camera going to lower apertures than f/4.9
Almost all IXUS series cameras do not have a real aperture (iris diaphragm), only a ND filter to "emulate" two F states...

With the forum search (look for "ND filter") you'll find more information about this...

* http://en.wikipedia.org/wiki/ND_filter
* http://chdk.setepontos.com/index.php?topic=2841.msg51106;topicseen#msg51106
* http://chdk.setepontos.com/index.php?topic=4141.msg40744;topicseen#msg40744
* http://chdk.wikia.com/wiki/ND_Filter
« Last Edit: 20 / June / 2011, 11:33:17 by fe50 »
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Offline whim

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Re: Aperture Override for IXUS 85/SD770
« Reply #2 on: 20 / June / 2011, 11:32:46 »
@maor1993

That's very simple: it's because ixus (with rare exceptions) don't have an iris diaphragm.
Instead, they use a ND (neutral density) filter, which can be manipulated from CHDK:
Extra Photo Operations -> ND Filter state
- Off  --> let Canon decide
- In   --> force filter in (use)
- Out --> force filter out (don't use)

See also: pdf User Guide, page 9

hth,

wim

edit: darn, out-typed by fe50 again ;)
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Offline maor1993

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Re: Aperture Override for IXUS 85/SD770
« Reply #3 on: 20 / June / 2011, 13:45:02 »
So what my camera displays as f/8 and f/11 and f/14 is just the nd filter?
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Offline reyalp

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Re: Aperture Override for IXUS 85/SD770
« Reply #4 on: 20 / June / 2011, 15:35:54 »
Quote from: maor1993 on 20 / June / 2011, 13:45:02
So what my camera displays as f/8 and f/11 and f/14 is just the nd filter?
The combination of zoom+ND filter, yes.
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