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setting chdk to establish control on F-number

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Offline naimenim

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setting chdk to establish control on F-number
« on: 21 / November / 2011, 10:05:35 »
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It may sound stupid, but..is there any way to set CHDK to establish control on my F-number. Sometimes, while shooting at macro mode, I want to keep this value to F/3.0 instead of F/5.8 as my camera's range is 3 to 5.8.

Is this value controllable? ???
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Offline waterwingz

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Re: setting chdk to establish control on F-number
« Reply #1 on: 21 / November / 2011, 10:13:46 »
If your camera has a controllable aperture,  there will be a menu item in the CHDK "Extra Photo Operations" menu called "Override Aperture Value"  that will allow you to do this. 

Can't tell from your user avatar what camera you have or I could be more specific.  Assuming you are using a A480,  there is actually not an adjustable aperature.  The camera uses a neutral density filter to change exposure values (in addition to the shutter speed).   You will also see changes in the f-stop reported when you zoom - but that's a function of the zoom lens optics and not a change in the iris.

see http://chdk.setepontos.com/index.php?topic=4670.msg48281#msg48281


« Last Edit: 21 / November / 2011, 10:22:41 by waterwingz »
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Offline srsa_4c

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Re: setting chdk to establish control on F-number
« Reply #2 on: 21 / November / 2011, 10:26:06 »
Quote from: naimenim on 21 / November / 2011, 10:05:35
It may sound stupid, but..is there any way to set CHDK to establish control on my F-number. Sometimes, while shooting at macro mode, I want to keep this value to F/3.0 instead of F/5.8 as my camera's range is 3 to 5.8.

Is this value controllable? ???
Your camera (A480) may not have the usual ND filter but a smaller aperture instead. That would explain, why the camera is choosing to use it in macro mode (it happens when there's plenty of light, I guess) - for a bigger depth-of-field.
If that is the case, you can force it in/out with the ND filter control in the "Extra Photo Operations" menu.
Pictures from the shutter assembly of the A430 are here: http://chdk.setepontos.com/index.php?topic=6551.msg69410#msg69410
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Offline naimenim

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Re: setting chdk to establish control on F-number
« Reply #3 on: 21 / November / 2011, 10:43:24 »
So, if my camera doesn't have aperture control feature, I won't be able to control it even with CHDK. I got it.
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Offline srsa_4c

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Re: setting chdk to establish control on F-number
« Reply #4 on: 21 / November / 2011, 10:52:52 »
Just try to force the "ND filter" out and then force it in while shooting in macro mode. Choose a subject on which the depth of field can be observed, and take a look at those pictures afterwards.

Update: it appears that the A470 and possibly later budget line models have also switched to real ND filters :(
« Last Edit: 19 / March / 2012, 21:10:01 by srsa_4c »
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