ETTR - page 2 - General Discussion and Assistance - CHDK Forum
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ETTR

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Offline reyalp

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Re: ETTR
« Reply #10 on: 04 / July / 2019, 15:41:27 »
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Quote from: pigeonhill on 04 / July / 2019, 10:03:52
As I say, if CHDK could over some of this functionality it would greatly add to its raw based capability.  Note I say raw based based, ie not jpegs.
Repeating myself
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In CHDK, you have to shoot an image to have access to full dynamic range raw pixel values.
(this is not necessarily an inherent limit, just describing how things actually are today)

Quote from: c_joerg on 04 / July / 2019, 02:08:37
Is get_live_histo RAW based?
No.
Quote from: reyalp
the relationship between viewport YUV pixels and raw values isn't specified AFAIK.
It's from the live view (same as used for CHDK histogram and zebra), which is some unspecified transformation from (presumably binned/subsampled at readout) raw to 8 bit YUV.

Maybe something like ML ETTR can be implemented in CHDK, maybe not. The only way it will happen is if someone decides to invest many, many hours of reverse engineering and coding.

You don't need to convince me or wateringz that it's a good feature.
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Offline pigeonhill

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Re: ETTR
« Reply #11 on: 04 / July / 2019, 15:45:26 »
@reyalp

Peace: I’ll say no more ;-)
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Offline reyalp

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Re: ETTR
« Reply #12 on: 04 / July / 2019, 16:12:12 »
Quote from: pigeonhill on 04 / July / 2019, 15:45:26
Peace: I’ll say no more ;-)
Sorry, I was a bit frustrated but I didn't mean to shut down the discussion, just make it clear where things stand.

The fact ML was able to implement a feature is a useful reference point, but in general, doesn't mean it can be easily added to CHDK.

It's also good know what features people who use CHDK would like to see. However, the few people who currently contribute generally aren't just sitting around looking for things to work on. The limiting factor isn't usually convincing us an idea is worthwhile, we already have many more worthwhile ideas than we have time to implement.

Finally, referring to the original thread: https://chdk.setepontos.com/index.php?topic=11576.0 it seems like you could implement ETTR for timelapse, as long as you are willing to use the previous exposure (or a throw away exposure) for metering with the existing Lua raw operations.  In fact, you can probably configure rawopint to do it.
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Offline pigeonhill

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Re: ETTR
« Reply #13 on: 04 / July / 2019, 16:38:56 »
@reyalp

No apology necessary.

I just recognise when I’ve said enough ;-)

BTW my use case is ‘just’ stills photography, not even timelapses.

I’m content with the current histogram, with a calibration step, although I wish the overexposure warning was clearer, ie I can hardly see it on my G7X.

But, as you say, yourself and other developers have a list to work through.

I’m more than happy with having CHDK on my G1X and G7X, and being able to run Lua scripts.

Cheers

Garry

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Offline reyalp

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Re: ETTR
« Reply #14 on: 04 / July / 2019, 17:35:39 »
Quote from: pigeonhill on 04 / July / 2019, 16:38:56
BTW my use case is ‘just’ stills photography, not even timelapses.
For scenes with relatively static lighting, the same approach could be used, someone would just need to write a script for it. Certainly something like your landscape focus bracketing script could add an extra shot for metering.

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I’m content with the current histogram, with a calibration step, although I wish the overexposure warning was clearer, ie I can hardly see it on my G7X.
Hmm, looking at mine I think the histogram over/under warnings are broken on digic 6. There is a smaller red dot that that shows when a peak overflows the vertical range, but for me the actual warning dots don't usually show up even with wildly incorrect exposure set in M mode.

For zebra, the limits are configurable and need to be moved significantly from the defaults, but the live view values used for histo over/under appear to be hard coded to use the 3 lowest and highest bins (weighted to the extremes) which basically never show up in the digic 6 live view.

I'll look into fixing / improving this.

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Offline srsa_4c

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Re: ETTR
« Reply #15 on: 04 / July / 2019, 17:56:46 »
Quote from: reyalp on 04 / July / 2019, 17:35:39
Hmm, looking at mine I think the histogram over/under warnings are broken on digic 6. There is a smaller red dot that that shows when a peak overflows the vertical range, but for me the actual warning dots don't usually show up even with wildly incorrect exposure set in M mode.

For zebra, the limits are configurable and need to be moved significantly from the defaults, but the live view values used for histo over/under appear to be hard coded to use the 3 lowest and highest bins (weighted to the extremes) which basically never show up in the digic 6 live view.

I'll look into fixing / improving this.
I think we'll need configurable black level and white level for live view. One of my D6 cameras uses approximately a 16...240 range (luma), the other one is approximately full range. This is when using the LCD, other output devices can potentially use different levels, I guess. I don't know whether pre-D6 cameras are affected.
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Offline reyalp

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Re: ETTR
« Reply #16 on: 04 / July / 2019, 18:42:56 »
Quote from: srsa_4c on 04 / July / 2019, 17:56:46
I think we'll need configurable black level and white level for live view. One of my D6 cameras uses approximately a 16...240 range (luma), the other one is approximately full range. This is when using the LCD, other output devices can potentially use different levels, I guess. I don't know whether pre-D6 cameras are affected.
I've had to adjust the zebra limits by a few to get useful results on other cams, but not nearly as much as d6 cameras. On both g7x and sx710, I found 20+ for both the under and over exposure thresholds was need to get useful zebra output.

We could (optionally?) use the zebra thresholds for the histogram warning.
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Offline pigeonhill

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Re: ETTR
« Reply #17 on: 05 / July / 2019, 13:08:46 »
@reyalp

On the road now, to Huntsville Alabama; in July, :-(

But will have my G7X with me :-)

I would certainly welcome you taking a look at the histogram. As you say, the histogram is broken somehow.

Cheers

Garry
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