Exposure Fusion and Intel Neo drivers

[Entropy512 (Andy Dodd)]

@"anon41087856

@Entropy512

As you your provided example - since I haven’t posted my patch yet (it’s become clear to me that all of the stuff currently hardcoded in DT needs to be exposed in the UI, and I admit I suck at UI/UX stuff), you just proved with your example that an exposure fusion workflow in linear space provides poor results, since that’s what darktable is currently doing.

Because this exposure fusion doesn’t happen in linear space at all

In the current code, it does, and it looks like garbage. Which invalidates your claim that linear operation is the One True Way. We’ll get to why that is in a bit.

, but after the base curve is applied, which is not linear and not even pure-power

Sure it is.

, and I tried to show you the code to justify my claim, but you still don’t understand.

A bunch of code not really relevant to a discussion of exposure fusion and how to make it operate better.

So it fails precisely because it does not happen in linear space. And you got your assumptions wrong because, as most opensource hackers, you treat RGB codevalues as random numbers and don’t look at the whole pipeline that goes from scene-linear light ratios to whatever broken transfer function you are trying to hack.

So, since you’re going to be highly insulting. You’re arrogant, overconfident, and repeatedly make claims that don’t stand up to reality. Over and over you say that operations in gamma space will cause chromaticity shifts and destroy colors, even when provided visual evidence that contradicts your claims. You are also apparently mentally incapable of discussing item B (exposure fusion) if it has ever been, in any way, associated with item A (basecurve) without bringing in your prejudices against A. (I’m not the one who shoved exposure fusion into the basecurve module. If you have issues with them being in the same modules, take that up with whomever did it, not with me.) You also seem to be ignoring the fact that Edgardo has been working on fixing the issues you’ve pointed out with the basecurve module (apparently you’re so prejudiced against it you’ve ignored the RGB norms work? And yes, I know that currently the fusion pipeline isn’t using his fixes, that’s become first on my TODO list before any further work, even though I’ve been eliminating that issue as illustrated above)

Again:

No chromaticity shifts when interpolating between the two brightnesses, despite your repeated claims it is guaranteed to happen.

As to luminance relationship at the “halfway” mark, you keep on forgetting about the fact that human vision is NOT linear.

I mean, if you want to invalidate Parseval’s theorem, do it. You might even get a Fields medal from it. Until you do, I’m right, you are wrong. You don’t blend, blur, convolve, feather, or merge anything outside of a linear space, where RGB codevalues are proportional to light energy. Full stop.

https://www.youtube.com/watch?v=LKnqECcg6Gw

You can rant about theory all you want. Then you need to remember that while it’s science-heavy, photography is partially an art form. And thus human perception is important.

So let’s try perception. All three images here were generated using the EXACT same settings (shown above). Tell me which one was weighted in linear and blended in linear, which one was weighted in gamma-2.4 and blended in linear, and which one was weighted and blended in gamma-2.4:

@Entropy512

For each of x=r, x=g, x=b - the relative relationship between r, g, and b will be preserved - see the gradient I posted as an example.

There is absolutely no relationship preserved between R, G and B at the output of the base curve, because it’s not linear, and it happens before the exposure fusion. Once again.
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Once again:

Exposure fusion and basecurve are only linked by the fact that someone jammed the functionality of one into the other. It’s well proven that the two can be decoupled, as shown in the image above. But you’re apparently incapable of preventing your prejudices against the prior state of basecurve (ignoring the recent work that’s gone into it) from causing you to froth at the mouth, see red, repeatedly state BASECURVE BAD BASECURVE BAD BASECURVE BAD BASECURVE AND ANYTHING EVEN REMOTELY ASSOCIATED WITH IT BAD, even when provided direct evidence that your claims being made don’t hold true when you get down to the most important thing - visual results to human eyes.

If you’ve got a recommended easy method for MEASURING the chromaticity shift you swear must be happening (e.g. prove that it’s actually happening), I’m all ears. (HSV decomposition in GIMP sorta works, but the 8-bit intermediary causes quantization errors and it’s just tedious… I will say that using that method, I’m not seeing fusion with blending and weighting in gamma space cause chromaticity shifts except in regions where the output luminance is near enough to black that quantization renders the result untrustworthy. But I’m amenable to a different measurement method.)