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Live Histogram

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Offline ewavr

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Re: Live Histogram
« Reply #10 on: 06 / June / 2008, 17:26:00 »
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Quote from: snapshot on 05 / June / 2008, 15:10:34
When taking pictures though, I've noticed that the live histogram is totally different from the histogram displayed with the picture on playback mode.

When I set histogram parameters:
mode=Y, linear
ignore boundary peaks=1
auto magnify=yes
then CHDK histogram is very similar to camera histogram (playback or live histogram in G7/S5)  (camera's histogram is much smoother).

Quote from: DataGhost on 06 / June / 2008, 17:05:32
Uhh... at least on the S5, in review mode the viewport is 'locked' to the last image on it. I don't know if it's possible to have the CHDK histogram on in review mode (never used that feature)

Really? In review (just after shoot) or in playback mode? In playback mode CHDK histogram and zebra must work...
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Offline fbonomi

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Re: Live Histogram
« Reply #11 on: 07 / June / 2008, 02:28:09 »
Quote
I remember noticing the dynamic range was always shorter in the playback histogram than the live histogram
snapshot, I think you missed that you have a lot of options on how the histogram is drawn: ignore boundary peaks, auto magnify, logarithmic scale etc (I can't be more exact on the details as my camera is now busy with a time-lapse:-).

Logarithmic scale would change a LOT the shape of the histogram, and auto magnify "zooms in" the histogram to better fill its area.

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Offline DataGhost

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Re: Live Histogram
« Reply #12 on: 07 / June / 2008, 05:55:28 »
Quote from: ewavr on 06 / June / 2008, 17:26:00
Really? In review (just after shoot) or in playback mode? In playback mode CHDK histogram and zebra must work...
When I switch my camera into review/playback mode, yes. The shutter also closes so it can't get any new live data anyway. If I disable display muting, I can see the live image stop until the camera is in playback mode... same with turning off the camera. It's probably something with the S5 if you're not experiencing it :)
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Offline cybercom

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Re: Live Histogram
« Reply #13 on: 07 / June / 2008, 13:40:39 »
@DataGhost:

FWIW, On the TX-1, I have a display of the histogram for each image in Playback mode which tracks pretty well with what I see when I take the picture in Record Mode. I just have to half-press the shutter to see the histogram. Zebra is also active.
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Offline DataGhost

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Re: Live Histogram
« Reply #14 on: 07 / June / 2008, 14:49:41 »
Hm, maybe it's rendered in the viewport buffer, then. That also happens in stitch assist mode.
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Offline cybercom

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Re: Live Histogram
« Reply #15 on: 07 / June / 2008, 15:49:31 »
Perhaps GrAnd or microfunguy have some insight into this. I know they were instrumental in getting the viewport buffer and display integrated into the TX-1 port.
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Offline snapshot

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Re: Live Histogram
« Reply #16 on: 10 / June / 2008, 13:20:42 »
Thanks everyone for the quick, interesting replies.  The reason for my original post was that the Live Histogram, in default mode, was showing a wider dynamic range, and a different shape for a scene than the histogram for that image in playback mode. It made me question whether I could trust what I was seeing.  I followed ewavr's advise, changing the Histogram parameters to Histogram layout = Y, Ignore boundary peaks = 1.  Now the Live Histogram is similar to the image histogram in playback mode. After viewing the images in Photoshop Elements, and comparing the images on screen and in camera with different histogram modes (RGB, Luminance), I'm convinced that my camera's playback histogram is in luminance mode.

snapshot
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Offline cybercom

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Re: Live Histogram
« Reply #17 on: 11 / June / 2008, 09:38:17 »
@snapshot:

So you're saying that playback is always in luminance mode regardless of the settings in CHDK?
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Offline snapshot

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Re: Live Histogram
« Reply #18 on: 11 / June / 2008, 15:26:40 »
Yes, I don't think CHDK has anything to do with the camera's playback mode.  When you make an exposure, then review the image in playback mode to check exposure, focus, etc, the histogram with the image appears to be a luminance histogram.  I say this only because it appears very close to the luminance histogram of the same image viewed in Photoshop Elements.  CHDK settings, of course, only affect the Live Histogram, when the camera is in record mode.

snapshot
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Offline cybercom

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Re: Live Histogram
« Reply #19 on: 11 / June / 2008, 21:08:05 »
Definitely worth knowing...

I applaud you!
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