ISO override not properly working. - General Help and Assistance on using CHDK stable releases - CHDK Forum
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ISO override not properly working.

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Offline Little9070

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ISO override not properly working.
« on: 31 / July / 2023, 16:53:36 »
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Hello! I'm having an issue with the override ISO setting on CHDK. On the stock Canon OS, I can select an ISO of 100, 200, 400, 800, and 1600 in manual mode, and on "Low Light" I can get an ISO of up to 6400 and on Auto (sometimes, iirc) 50. Yet, when I try and override my ISO to anything that isn't 100, 200, 400, 800, and 1600, It just snaps to one of those values. If I set my ISO on the override menu to 50, it snaps to 100 when I take the photo. Same with 6400 snapping to 1600. If I could get some help and a possible solution, that would be very helpful. Thanks!
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Sent from my Canon PowerShot SX410 IS
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Offline blackhole

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Re: ISO override not properly working.
« Reply #1 on: 01 / August / 2023, 03:09:49 »
Quote from: Little9070 on 31 / July / 2023, 16:53:36
Hello! I'm having an issue with the override ISO setting on CHDK. On the stock Canon OS, I can select an ISO of 100, 200, 400, 800, and 1600 in manual mode, and on "Low Light" I can get an ISO of up to 6400 and on Auto (sometimes, iirc) 50. Yet, when I try and override my ISO to anything that isn't 100, 200, 400, 800, and 1600, It just snaps to one of those values. If I set my ISO on the override menu to 50, it snaps to 100 when I take the photo. Same with 6400 snapping to 1600. If I could get some help and a possible solution, that would be very helpful. Thanks!
If you are talking about the SX410 camera, the ISO override is limited to values within the range used by the camera in manual selection mode. This is because selecting any value outside of the original range in combination with flash causes a crash.
The camera can still automatically select any value, depending on the selected shooting mode.
If you want to get rid of this limitation, delete this two lines  in the platform_camera.h file
Code: [Select]
#define CAM_MIN_ISO_OVERRIDE 100
#define CAM_MAX_ISO_OVERRIDE 1600and compile your own version of CHDK.
The problem is probably related to the gain of the sensor, but this has not really been investigated.
In any case, if you are going to move the limit for ISO override, you do it at your own risk, no one knows if it can cause any bigger problems.
I personally didn't encounter any additional problem if I don't use flash, but I also don't see any practical benefit of using an ISO value higher than 1600 unless you want to use a short exposure time in low light conditions.
This is actually used by the camera in Low light shooting mode, but at a low resolution to cover up excessive chroma and luminance noise.
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