Curves behaviour changed (in development version)

(Samuel Chia) #1

Hello everyone,

I’ve noticed that the curves tool in custom mode has changed in behaviour. In V5.4 stable release, it behaves like any other curves adjustment tool I’ve used, most notably Photoshop. When I place a control point in the shadow region (<50%) and raise it, the upper section of the curve gets pushed upwards a lot and one has to watch out for highlights getting clipped and usually will have to add another control point in the highlight section to roll off the curve there.

I’m also playing with one of the more recent developmental versions, and when doing the same, the upper section of the curve hardly moves at all when I push up the shadows. The same is true in the opposite direction for a control point in the highlights section.

Just wondering what’s going on and I’m not sure how to really feel about this change yet. On the face of it I dislike the new curves behaviour almost all of the time, such as when placing multiple control points which results in kinks compared to the previous way it used to work. For instance, a simple shadow compression and midtone contrast boost with both methods. Please refer to the attached screenshot. The old style has a smooth gradual change in the gradient from less than one to more than one. The section between the two added control points is nice and smooth.

The new style has the gradient change quite drastically within those two points. To achieve the same shape, a third point must be added to raise the highlights, but upon closer inspection, the kink in the shadows still somewhat remains.

If there are any advantages to this new curves behaviour, I would like to learn. I do notice that when adding a new control point and moving it, the entire curve (especially if held down by other control points) moves less than the old curves design. Perhaps the intention is so that more precise/targeted adjustments can be made with fewer overall control points?


RawTherapee 5.5 is one week away
(Franz Trischberger) #2

See this issue for reference:

(Samuel Chia) #3

Thank you @ff2000, that was very helpful to me.

(Alberto) #4

Hi @samuelchia,

Yes, this is exactly the point. The new behaviour gives you more control on the overall shape of the curve, because control points have a more “local” effect.

I can only repeat what I wrote on github: for me there’s no problem to revert to the old behaviour, if there is consensus on this. What I will (personally) not do is introduce yet another curve method to RT, not because I think it’s conceptually wrong, but simply because I don’t have the interest in doing so…

Hope this helps

(Andrew) #5

I noticed this too, and created this issue in October.

I think both the old and new curve have their pros and cons. I am a little uneasy that the new one is not so smooth, perhaps a bit too localised. Anyway, @Morgan_Hardwood says
“I wouldn’t mind having the old mode added as an option to the combo, but I like the new curve mode and would like it to remain.”
So perhaps this could be done if enough people want it?

(Simon Frei) #6

In general I really want backwards compatibility and tone curves are the main tool I use in Rawtherapee. So I loaded an image I have done in 5.4 with 5.5-rc1 and the result is clearly different. One tone curve is clearly different between them, the other looks very similar. In addition the histogram in the background of the tone curve looks different, so there might be another factor changing the result.

In any case the new curve will be different, otherwise what’s the point of introducing it. So purely in my opinion the old method should be kept around for backwards compatibility. This is purely a request though, I know it is super annoying for development to keep “legacy” stuff around. And from a recent discussion (can’t remember what) I got the impression that pp3 backwards compatibility isn’t guaranteed anyway, so I might be flogging a dead horse. Again I am not demanding, just stating my opinion. I am happy to have such a great tool and know from own experience how much time that goes into development (and that doing no features is soooooo much more fun than *** like backwards compatibility or transitions :wink: ).

Also completely unrelated: It’s a bit confusing that there are no builds on the RC tag on github. I had to search for the dev builds thread here in the forum to discover the nightly tag on github, that has RC builds. Also the download page on doesn’t have it, but I seem to remember that site is scheduled for a revamp by pixls own ghost…websitebusters team.

If it is of interest, that’s the file and pp3 I was talking about - I hope the pp3 is still the unchanged original one (the pic or edit were not picked for their quality).
20181110_101705-JO_Jubilaeumsfest.arw (15.8 MB)
20181110_101705-JO_Jubilaeumsfest.arw.pp3 (10.7 KB)

For posterity:
I hope nobody noticed the incorrect “I am demanding” before I could edit it to “I am not demanding” :flushed:

(Samuel Chia) #7


Thanks @agriggio for confirming my guess.

I agree with @RawConvert, both have pros and cons. I followed the thread on Github and thought (and played) about the CTRL+Left Click issue, and I agree that this aspect of the new curves behaviour isn’t optimal from a UX perspective. Adding a new point should not also change the curve’s shape, however the new curves spline algorithm does not allow for that. It is not right or wrong behaviour, just unexpected and therefore disturbing until it is accepted. Yet intuitively, it doesn’t feel normal to me.

For simple S-curves, the old curve mode is better for sure. For complex curves, the new curve mode is probably better. I rarely apply complex curves to my images - it hurts them more than it helps almost always. It might be too much to ask but maybe it would indeed be possible to have them both.

Edit: Oh I see @rasimo 's new post. Yes! Yes! Backwards compatibility is so important. If the new curves mode is to be implemented, the old mode should also be an option. “Custom” and “Custom (legacy)” perhaps…

(Franz Trischberger) #8

I found the 5.4 curves hard to use. Moving one point changed the entire curve, editing was a continuous forth and back. At some point I started to only use “parametric”. The new curve is way easier to use IMO. But I still use parametric for quick’n’easy edits.
Adding the old curves back as a fifth option of course would please all of us :slight_smile:

(Sebastien Guyader) #9

I personally prefer the new curve behavior. I really hated that adding and moving one point in the shadows had such a global effect on the whole curve, and I often had to add a point just to compensate for the effect of the previous. I feel it more intuitive to have a more local effect as in the current implementation.