Author Topic: Hypothesis about HDR  (Read 446 times)

bpv5P

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Hypothesis about HDR
« on: April 03, 2017, 05:27:32 AM »
Just as an hypothesis: now that some cameras can do 60fps on MLV, would it be possible to intercalate exposures between frames, kinda like the old HDR video feature?
This could be a interesting project, since the resulting footage could be processed using the ZeroNoise technique (using software like the HDRMerge - very slow, but still), to get a 24bit footage with better dynamic range and less noise...
This footage could then be processed on, say, Rawtherapee and with the use of "dark frames", the footage would have a great SNR.

Now the problem I see is: on the old HDR feature, if I remember correctly, the ML used the ISO settings to get different exposures. That wouldn't be possible with ZeroNoise, since it uses something like noise avaraging[1] to get the noise pattern, from what I understand.
So, it would be needed to change the shutter speed or the lens aperture (for non-manual lenses - if that's even possible on ML). The first would generate ghost images in high speed objects and the letter would turn the feature to be useless for everyone using manual lenses.

Anyway, could be a interesting idea to some developer. Just wanted to share.




[1] http://www.cambridgeincolour.com/tutorials/image-averaging-noise.htm

a1ex

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Re: Hypothesis about HDR
« Reply #1 on: April 04, 2017, 09:58:44 PM »
You gave me an idea: it *might* be possible to alternate a short exposure with a 360-degree one, therefore ending up with two adjacent exposures (in time). Something like this:

Code: [Select]
|------frame 1-----||-----frame 2------||-----frame 3------||-----frame 4------|
[...blanking....][s][looooooooooooooong][...blanking....][s][looooooooooooooong]...
|------------HDR frame 1---------------||-------------HDR frame 2--------------|

where "blanking" means the sensor is not capturing light, and "s" is a short exposure.

which would definitely result in ghosting in moving subjects, but at least the two "motion blurs" should be adjacent (with little or no gap between them).

That's just theory based on my current understanding of LiveView, but didn't try.

DeafEyeJedi

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Re: Hypothesis about HDR
« Reply #2 on: April 04, 2017, 10:16:05 PM »
Holy moly this is tempting...
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bpv5P

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Re: Hypothesis about HDR
« Reply #3 on: April 05, 2017, 02:04:44 AM »
Seems a interesting idea a1ex. I have no advanced programming skills to do it, but I can compile ML and do all necessary tests on 600D if you're willing to put some effort on it.
I think the adtg research is pretty interesting, but the DR and SNR enhancement would be minimal. On this ZeroNoise the enhancement would be pretty clear, I think. It may not be something you would use for everyday work, but that's certainly a great feature for people doing low-budget film.
Thanks for all the work.

bpv5P

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Re: Hypothesis about HDR
« Reply #4 on: April 05, 2017, 02:35:18 AM »
Actually 600D can't do 48fps on a usable resolution, but I could try to get a MKIII just to test it.

otherman

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Re: Hypothesis about HDR
« Reply #5 on: April 05, 2017, 09:25:07 AM »
Dual ISO make the same thing without ghosting, am I correct?
24bit hdr raw video? Is there something on the market capable of this?
It's seams a gymnastick thing, but... Why not!
Port it to eos-m please  :P

bpv5P

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Re: Hypothesis about HDR
« Reply #6 on: April 05, 2017, 11:09:44 AM »
Dual ISO is not the same. The image has half the resolution. It could generate FPN. If can make moire even worst. It has to suffer a interpolation to function.

The proposed solution would have the entire resolution, and could be processed with the ZeroNoise, which would result in better dynamic range and less noise (greater SNR).

You could compare still images: take a picture using dual iso. Then take other two pictures in the same place, but with different exposures.
Use cr2hdr to process the dual iso file. Then, use HDRMerge[1] to process the other two pictures. Open on some raw processor and see the results for yourself. Fewer noise, full resolution and better DR.

[1] https://jcelaya.github.io/hdrmerge/

 

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