I need help with (Tv) (Av) & (Sv) values equivalents to Shutter/Aperture/ISO - General Discussion and Assistance - CHDK Forum
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I need help with (Tv) (Av) & (Sv) values equivalents to Shutter/Aperture/ISO

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Offline Alejandro

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I need help with (Tv) (Av) & (Sv) values equivalents to Shutter/Aperture/ISO
« on: 02 / December / 2011, 19:13:20 »
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Let me see if i understand this correct,
cause i'm a little confuse.

I'm testing this script for Manual Video Controls in my SX40,
but i have no idea how Tv/Av/Sv values translate into Shutter/Aperture/ISO

My question is:
If i set my (Tv) to a certain value, let's say 540...
but i change my (Sv) values from shot to shot...
does that mean that my shutter speed is changing every time?

Or this values are totally independent from each other?

Depending on the case...

can anyone help me translate the values equivalents for Shutter, aperture & ISO?



Alejandro.

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ELPH 300HS (IXUS 220)
EOS Rebel T3 (not T3i)
EOS 7D
SD770 IS
SX40 HS
SD1300 IS
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Offline waterwingz

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Re: I need help with (Tv) (Av) & (Sv) values equivalents to Shutter/Aperture/ISO
« Reply #1 on: 02 / December / 2011, 19:23:52 »
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline Alejandro

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Re: I need help with (Tv) (Av) & (Sv) values equivalents to Shutter/Aperture/ISO
« Reply #2 on: 02 / December / 2011, 22:25:02 »
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The moderator got his message.
« Last Edit: 03 / December / 2011, 08:07:58 by Alejandro »
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ELPH 300HS (IXUS 220)
EOS Rebel T3 (not T3i)
EOS 7D
SD770 IS
SX40 HS
SD1300 IS
*

Offline reyalp

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  • 14125
Re: I need help with (Tv) (Av) & (Sv) values equivalents to Shutter/Aperture/ISO
« Reply #3 on: 03 / December / 2011, 00:15:20 »
 ::)

Anyway, just in case someone else has this question, the cameras generally work in APEX*96 values.

An excellent description of APEX can be found at  http://dougkerr.net/Pumpkin/#APEX

Canon firmware use the 96 multiplier to allow calculations to be done with integers. CHDK scripts functions generally also work in these units.

Sv, Tv, Av values are completely independent, adjusting one does not affect the others. However, you can use the APEX equation to calculate how much you should change one to compensate for a change in another.
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