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RAW Develop problems on SX230 HS

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Offline waterwingz

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Re: RAW Convert problems on SX230 HS
« Reply #10 on: 07 / April / 2013, 10:32:56 »
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Quote from: sx230user on 07 / April / 2013, 10:01:18
With i-contrast off all my versions of CHDK now create jpgs without ghosts or other problems.  Thanks.  Just curious, do you know why i-contrast causes this?
Based on a discussion on the CHDK IRC channel last night, reyalp's guess is that Canon does some processing of the RAW image buffer prior to the point at which CHDK is normally hooked in.  If the image processing software decides that  some level of detail might be washed out,  and i-contrast is set to AUTO mode, then it subsequentially uses that information for image enhancement when it creates the JPG.  That processing occurs after the CHDK RAW hook has completed and nence the imprint/shadow you were seeing.

Obviously, to fix this in CHDK without user intervention,  it would be necessary to figure out how to disable i-contrast when using RAW develop or find the buffer that the i-contrast information is stored in and clear it prior to RAW develop.

For now,  the easier fix is to just disable i-contrast immediately prior to using RAW develop.
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Offline sx230user

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Re: RAW Convert problems on SX230 HS
« Reply #11 on: 07 / April / 2013, 11:52:39 »
Quote from: waterwingz on 07 / April / 2013, 10:32:56
Quote from: sx230user on 07 / April / 2013, 10:01:18
With i-contrast off all my versions of CHDK now create jpgs without ghosts or other problems.  Thanks.  Just curious, do you know why i-contrast causes this?
Based on a discussion on the CHDK IRC channel last night, reyalp's guess is that Canon does some processing of the RAW image buffer prior to the point at which CHDK is normally hooked in.  If the image processing software decides that  some level of detail might be washed out,  and i-contrast is set to AUTO mode, then it subsequentially uses that information for image enhancement when it creates the JPG.  That processing occurs after the CHDK RAW hook has completed and nence the imprint/shadow you were seeing.

I've been curious about how i-contrast works.  It seems like you're saying that in Shoot mode when i-contrast is set to Auto in the Menu it is similar to how a user would PP a RAW file before turning it into a jpg, it's a process during RAW development.  When using i-contrast in Review mode however it's clearly a manipulation of the original jpg.  In principal then, without regard to other pluses and minuses of i-contrast, if one had the sense before a shot that the scene would benefit from it then he'd end up with a cleaner jpg if enabled in the Menu for shooting rather than applying it in Review after the fact.  Am I understanding this correctly? Would the same logic apply to My Colors processing?

When I get a chance I'm going to experiment to see if a difference between the two ways of applying i-contrast can be seen,  but understanding the camera's operation is interesting as well.
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Offline reyalp

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Re: RAW Convert problems on SX230 HS
« Reply #12 on: 07 / April / 2013, 14:49:22 »
Quote from: sx230user on 07 / April / 2013, 11:52:39
In principal then, without regard to other pluses and minuses of i-contrast, if one had the sense before a shot that the scene would benefit from it then he'd end up with a cleaner jpg if enabled in the Menu for shooting rather than applying it in Review after the fact.
Probably, since we now know for sure that the shooting mode version isn't just applying the same post-processing as in playback. When you use i-contrast in shooting mode, the camera has a full 12 bit raw buffer to work with. If you do it on the jpeg, some precision and/or dynamic range must already have been lost.
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Would the same logic apply to My Colors processing?
Hard to know for sure, but doing it in the shooting process certainly has the potential for a cleaner result.

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When I get a chance I'm going to experiment to see if a difference between the two ways of applying i-contrast can be seen,  but understanding the camera's operation is interesting as well.
Some review sites may have already done this, I remember reading some dpreview reviews where they tested the i-contrast, but I don't recall if they compared the playback and shooting versions.

I would suggest using a tripod to take identical scenes, difference the resulting images, and then crank up the contrast.
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Offline reyalp

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Re: RAW Convert problems on SX230 HS
« Reply #13 on: 07 / April / 2013, 14:56:55 »
Quote from: waterwingz on 07 / April / 2013, 10:32:56
Based on a discussion on the CHDK IRC channel last night, reyalp's guess is that Canon does some processing of the RAW image buffer prior to the point at which CHDK is normally hooked in.
To expand on this slightly my guess is that it works something like this
1) shot fills raw buffer
2) Canon firmware processes the raw buffer to create a new "i-contrast buffer" with brightness information
3) raw hook (in the case of raw develop, loads totally different data into raw buffer)
4) Canon firmware creates jpeg, applying the data from #2 in some way.

If we found the "i-contrast buffer", there might be interesting uses for it.
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Offline waterwingz

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Re: RAW Convert problems on SX230 HS
« Reply #14 on: 07 / April / 2013, 15:03:32 »
Quote from: reyalp on 07 / April / 2013, 14:56:55
If we found the "i-contrast buffer", there might be interesting uses for it.
Or if we find where the Canon firmware checks to see if i-contrast is enabled,  we could simply patch that out during Raw Develop processing.
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