Histogram EXP indicators always on. - General Help and Assistance on using CHDK stable releases - CHDK Forum
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Histogram EXP indicators always on.

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Offline Graystar

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Histogram EXP indicators always on.
« on: 04 / May / 2008, 23:44:05 »
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(Allbest build 50, Canon A710 IS)

When I enable the histogram EXP function it, it always displays the indicators regardless of the histogram.  I tried other versions and found this happens in GrAnd 148, Allbest 37, and Allbest 50 (the only three I've tried.)  Does anyone else have this problem?  Maybe it's unique to the A710?

Or maybe I'm understanding this function incorrectly.  I thought that then you enabled Over/Under EXP that the "EXP" and the red dots would only appear then there's under or over exposure in the scene.  Is this correct?

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Offline vine

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Re: Histogram EXP indicators always on.
« Reply #1 on: 05 / May / 2008, 03:40:13 »
Have you tried increasing the value of Ignore boundary peaks?
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Offline Graystar

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Re: Histogram EXP indicators always on.
« Reply #2 on: 05 / May / 2008, 07:12:16 »
Yes I tried adjusting that value and it didn't do anything, which is what I expected.  The Ignore boundary peaks setting affects how the histogram appears, and doesn't have any relationship to the over/under indicator.
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Offline Graystar

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Re: Histogram EXP indicators always on.
« Reply #3 on: 05 / May / 2008, 07:24:34 »
Okay I have some more information now that the sun has come up.  I can get it to work in daylight street scenes.  The image in my previous post was taken indoors under tungsten light.

It seems like the EXP indicator will appear if one of the color channels is clipped, even though it doesn't look that way in the RGB or Y histograms.  It also looks like the white balance setting has an affect on the histogram (as it should, since the histogram goes by the JPEG result...not the RAW result.)  I need to test some more to see exactly what is causing this.
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Offline Graystar

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Re: Histogram EXP indicators always on.
« Reply #4 on: 05 / May / 2008, 20:32:58 »
I've discovered the conditions that cause the problem.  On an A710 IS, when the A/V Out terminal is being used, the CHDK histogram will always indicate over and under exposure.  I don't know if this happens for other cameras.
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Offline PS

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Re: Histogram EXP indicators always on.
« Reply #5 on: 06 / May / 2008, 15:01:43 »
Actually the histogram you posted looks clipped (small peaks at both boundaries) so it works as 'advertised'.
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Offline Graystar

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Re: Histogram EXP indicators always on.
« Reply #6 on: 06 / May / 2008, 15:55:27 »
Quote from: PS on 06 / May / 2008, 15:01:43
Actually the histogram you posted looks clipped (small peaks at both boundaries) so it works as 'advertised'.

But there's nothing in the image to cause the clipping.

As I said already...if I disconnect the A/V cable then it works properly.  So there's something about A/V output that causes the problem.
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Offline PS

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Re: Histogram EXP indicators always on.
« Reply #7 on: 06 / May / 2008, 16:11:34 »
Quote from: Graystar on 06 / May / 2008, 15:55:27
As I said already...if I disconnect the A/V cable then it works properly.  So there's something about A/V output that causes the problem.
I confirm that with A610.
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