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Disable RAW based on image quality

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Offline Mirfak

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Disable RAW based on image quality
« on: 04 / September / 2008, 19:48:57 »
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One of the great features in the new builds is the ability to disable RAW capture under certain conditions.  These conditions are based on shooting modes that you may not want slowed down by RAW capture.

I was thinking that it might be useful to extend the functionality to include selecting or disabling RAW base on image quality (or perceived quality) e.g.

1) Turm off RAW capture if selected ISO (manual or Auto) is below a user selected value.  If, for example, I'm happy with only JPEGs below ISO 200 (because the in-camera NR is acceptable below this level), turn off RAW capture.
2) Turn off RAW capture if shutter speed is higher (or lower) than a certain value.  For example, noise increases at slower shutter speeds, so I may want to use RAW only for the slower shutter speeds (e.g. under 1 sec).
3) Turn off RAW if dynamic range of scene is below a certain range.  The idea is that if the captured dynamic range is within the camera's capabilities, then turn off RAW.  Otherwise, turn on RAW (so I have a chance to recovery marginally blown highlights in PP).  Now I don't know if there's a way to record the dynamic range (there's currently no OSD showing this) and even if were possible to determine, dynamic range is ISO dependent (lower dynamic range at higher ISO speeds).  Hmmm, may have to forget this one....
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Offline PhyrePhoX

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Re: Disable RAW based on image quality
« Reply #1 on: 06 / September / 2008, 17:24:37 »
will think about a way to implement this
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Offline Mirfak

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Re: Disable RAW based on image quality
« Reply #2 on: 08 / September / 2008, 10:34:57 »
One final thought on this issue.  It occurred to me that another important factor in considering noise is sensor temperature.  Except for the astrophotographers out there, typical camera reviews don't consider this factor.  One way to assess the sensor temperature effect on noise in a somewhat controlled manner would be in an air-conditioned environment where you can vary the ambient temperature and look at the image noise at various ISOs.  As a real world example, on a fall day where the outside temperature is 5degC, I might have less image noise at ISO 400 than at ISO 200 in summer when the temperature is 28degC.

Given that we can now measure the sensor temperature in CHDK, a useful possibility for RAW capture would be to base the RAW capture on both ISO *and* sensor temperature.  However, this would require a lookup table and might vary from camera to camera.  Major concern is processing time to go through all the RAW capture checks (including the ones that already exists). Anyway, some food for thought.
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Offline PhyrePhoX

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Re: Disable RAW based on image quality
« Reply #3 on: 08 / September / 2008, 11:22:53 »
well, temperature is used by the camera to decide if it shall take a darkframe, so on high temperatures a darkframe is taken even though the shutterspeed isnt 2 seconds (but shorter).
well, maybe we can even use temp checks in raw code, but i'd like you to make some tests first ;)
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