Hi @jandren thanks for the hard work!
It would be possible to reintroduce a little amount of hue shift in this case?
The preserve hue option preserve the hue and saturation ( saturation = max rgb - min rgb), it only interpolates the middle rgb value, however it reduces a little the luminance.
This is the reason why very bright orange could be a little off.
Using something like 70%-75% preserve hue and 30% - 25% rgb is visually the same correct hue but it handles better sunset photos.
Yes! I have been toying with this idea myself
Haven’t had the time to test it yet though, just some scribbles in my idea notebook. I had liked to go one step further and make it adjustable as a function of scene luminance. Middle grey could then be 100% corrected while very bright pixels converges to some percentage of crosstalk.
If you know about anyone doing something like that in a paper or similar, please share!
Uhm i need more time to ready carefully this paper, i think it describes two steps
restore hue after a per-channel tone rgb mapping , hue and saturation are the same of hsv/hsl color model…
This is exactly what the preserve hue ( film like in rawtherapee) does.
restore somehow the luminance channel (from the per-channel rgb tonemapped image?)
Interesting settings that may be close to a rather bland JPG output. I am rather surprised that some users are trying to emulate the JPG style … I thought that the entire reason that we shot RAW was to have the ability to put a personal stamp on our images.
I noted that when playing around with the image that I think @davidvj shared. It had a lot of chromatic aberrations in the foliage. I wanted to compare darktable to ART or RT as they can use DCP files just to see what was up using that for color management and I think there are 3 options in ART/RT from the DCP profile , tone curve Base table and look table. Disabling the base table in color management dramatically improve the CA. I’m not sure how the overall colors fared but clearly there are tweak and ways that things are potentially altered before it gets to the tone mapper…
I’m not quite sure if that phrasing is a correct assertion. Starting points are just that…a start. The ability to put a personal stamp on sth. is tangential to the question of what is a starting point. This particular setting was derived from the question “can filmic and sigmoid be matched”. The answer to that is: in many cases no. @pass712 found a close match and he shared it. (If I understood his posting as he intended)
Likely as well referring to the jpg as a common frame of reference for points of discussion and comparison of the two methods rather than necessarily trying to match it???
@davidvj@PhotoPhysicsGuy I may have been the person who gave the impression that I was trying to emulate the OOC jpg output. I just said that the tonality was similar to the OOC jpg, but that is just a starting point. Something bland with no unpleasant surprises works as an initial setting for me.
I know that this is somewhat away from the original discussion but … I simply ignore this ‘base’ JPG view (whatever that is) and use presets to go directly to my personal style. To me any JPG style is simply a distraction from my vision.
I use a Fujifilm camera so JPG can be any number of the manufacturer’s diverse visions.
I personally think the best starting point for discretionary editing is the linear RGB right after demosaic. I’ve had cases where the exposure and the scene worked out to need nothing beyond that, no tone curve required.
I agree, editing depends on the result you want to achieve and the point where you started. Sometimes both are close together.
I would always prefer a starting point which is close to my result so that I can reduce my time for editing to a minimum. And of course, the way and effort to reach your result also depends on your skills.
If editing is a lower priority (and believe me, I get that), I think that’s a decent approach to photography.
I used to handle things that way, but I came to realize what I was doing in a lot of cases was to apply a tone curve that reversed the effect of the “base” curve, or whatever was applied to get the first notion of “result”. And that slewing of the image data first one way, then the other, just accumulates hue shift that can eventually become noticeable if you lay curve upon curve.
If you realize that and take care with how many tone curves you lay in the workflow (and don’t forget the last of those which is the display/export color profile, which we tend to forget about), you can get decent results. Just realize that every tone curve in the workflow adds to the hue shift…
This first Hue paper was interesting. I would summarize it in the following way:
Reduce dynamic range using rgb ratio
Introduce hue shifts following the Bezold–Brücke effect
Map out of gamut colors to the display saturation boundary
Here is a good illustration from handprint : colormaking attributes
(That page has a ton of other stuff to digest as well at a later stage)
If I read the diagram correctly, this effect is similar to what we get with the crosstalk option. It is at least in the same direction. This would explain why it seems natural that bright objects shift like this.
They are not focusing on the problem of out of gamut saturation, it’s just very shortly mentioned. So I’m a bit hesitant to conclude that from this paper.
The second paper is more involved and it, more importantly, includes local effects for the tone mapping. I’m currently working with the hypothesis that most local effects are better dealt with as separate modules earlier in the darktable pipeline.
And finally, that post by sankos you linked @afre has some interesting links that finally took me all the way to a small open-source software called dcamprof. A single man effort in trying to make profiles that are as correct as possible for later use in image editing pipelines. Tried to have a look at the code and it seems like his approach is based on what I have named preserve hue. He names it after the fact that it seems to be used in the Adobe dng tone curve. This result is then modified to match saturation from the original picture and some hue adjustments are finally applied to the highlights. These include making red colors more yellow for pleasing sunsets. Again similar to the effect with crosstalk but just for a selected range of colors.
