D10 build 2798 ISO override problem (ISO > override) - General Help and Assistance on using CHDK stable releases - CHDK Forum
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D10 build 2798 ISO override problem (ISO > override)

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Offline andyroo

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D10 build 2798 ISO override problem (ISO > override)
« on: 06 / June / 2013, 16:39:19 »
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I am having a weird problem in scripts and just shooting where as far as I can tell the ISO in override is getting set higher than I set it to. the weird thing is, I can see the ISO showing my setting in the upper left until it takes the picture, then it advances to the higher value right when I shoot.

for example, right now if I hold the trigger on half-shoot I can see the ISO 100 change to ISO 160 (canon white letters) while the CHDK overlay still says ISO in red letters.

My "Extra Photo Operations" settings are:

Disable Overrides [Off] (does the same in [Disable]
Include AutoISO & Bracket [ ]
Override Shutter Speed [1/1250]
ND Filter State [out]
Override subj Dist V [193731]
Override ISO Value [10]
Value Factor [10]
Custom Auto ISO menu not enabled.
quality override [sup.fin]

nothing else adjusted

 I was using an old build (1798 I think) and updated to use the LED functionality since I have screen-off delays in scripts now. but now I have to troubleshoot the ISO.

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A720 1.00c | D10 1.00b |SX220 1.01a | SX230 ? | SX30 1.00p CHDK ver. 1.1.0-r1727
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Offline waterwingz

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Re: D10 build 2798 ISO override problem (ISO > override)
« Reply #1 on: 06 / June / 2013, 17:07:53 »
This question comes up every month or so.  What you are seeing is the difference between Canon's "marketing" ISO values and the internal real ISO values that CHDK uses.

Esssentially,  Canon tries to calibrate their ISO values against their interpretation of what the equivalent ISO setting for 35 mm film would have been.   CHDK uses an ISO value that balances the internal exposure calculations using  Tv, Sv, Av, and Bv ( shutter, sensitivity, aperature, luminance).

Typically, the Canon value will be higher than the CHDK value.   More info here :  http://chdk.wikia.com/wiki/CHDK_User_Manual#Override_ISO_value   or search this forum for Market ISO.
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Offline andyroo

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Re: D10 build 2798 ISO override problem (ISO > override)
« Reply #2 on: 07 / June / 2013, 00:49:34 »
Did the way that CHDK handled this in the last few months change? When I upgraded to the most recent build, my ISO values went up, and I ended up with a couple flights that were bled out from over exposure. I had to back down the ISO further than I have had it in the past in order to get the same exposure.

 Also in my previous flights, the ISO in the EXIF that was consistent with the setting I had in the overrides. Now the ISO is higher than the overrides.
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Offline waterwingz

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Re: D10 build 2798 ISO override problem (ISO > override)
« Reply #3 on: 07 / June / 2013, 09:20:08 »
Quote from: andyroo on 07 / June / 2013, 00:49:34
Did the way that CHDK handled this in the last few months change?
I don't believe there was a change in how this is done but reyalp (who also has a D10 coincidentally) would likely remember better that me. 
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline reyalp

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Re: D10 build 2798 ISO override problem (ISO > override)
« Reply #4 on: 07 / June / 2013, 17:37:10 »
Quote from: andyroo on 07 / June / 2013, 00:49:34
Did the way that CHDK handled this in the last few months change?
I'm pretty sure it hasn't. What version are you using now ? If you can find out it would also be useful to know which version you were using before.

Quote
Also in my previous flights, the ISO in the EXIF that was consistent with the setting I had in the overrides. Now the ISO is higher than the overrides.
I would strongly suspect that something else in your environment or settings has changed.

To my knowledge, ISO overrides on the D10 have always worked in "real" ISO values.
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Offline andyroo

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Re: D10 build 2798 ISO override problem (ISO > override)
« Reply #5 on: 14 / June / 2013, 16:00:41 »
I am using build 2798 now. I was using build 1727.

So from what you are saying, I shouldn't see the "Canon-style" (white text) ISO value flash up to 160 when I have the overrides set at 100 showing up as ISO 100 on the red CHDK overlay text?

I definitely didn't change anything else on purpose. I used the autobuild for 2798 because I couldn't get it to compile in CHDK-Shell. For 1727 I build it from CHDK-Shell.

Andy
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Offline reyalp

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Re: D10 build 2798 ISO override problem (ISO > override)
« Reply #6 on: 14 / June / 2013, 16:41:05 »
Quote from: andyroo on 14 / June / 2013, 16:00:41
So from what you are saying, I shouldn't see the "Canon-style" (white text) ISO value flash up to 160 when I have the overrides set at 100 showing up as ISO 100 on the red CHDK overlay text?
No, I'm not saying that at all. I see the same thing on my D10, and this is expected because the override works in "real" units and the Canon display works in "market" units. If you want a "market" ISO of 100, you should override to something around 70.

I quite sure this has not changed since I did the D10 port.
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