Any interest in a "film negative" feature in RT ?

[nonophuran]

@rom9

@nonophuran

would you mind telling me more about the filmneg white balance sliders? are they exactly on the same orthogonal axes as the usual sliders?

Not exactly. The sliders are imitating the behaviour of the normal WB tool, so the blue/yellow slider doesn’t go straight from yellow to blue, but instead follows the planckian locus … i think… well, don’t trust me on these scientific topics , the point is that RT provides a very handy utility class that easily converts between color temperature + green equalisation to a set of RGB multipliers.
I used that utility in order to have 2 sliders behaving the same as the normal WB, in the hope to make the process more familiar to the user.
The key difference is that i do not show an absolute color temperature value (it wouldn’t make sense as it has no correlation to the actual illuminant of the original scene), but instead i’ve made a very generic and vague “compensation” slider: if you leave it centered at zero, your spot stays neutral gray; if you move it left or right, you make the image cooler or warmer.
Regarding the magenta/green slider, that should be a simple green multiplier.

ok, I think I get it. I’m not 100% sure but it looks like both axes are decorrelated (orthogonal).
What I meant to say in the link I shared about the tilt is that:

• either you have: one blue / yellow axis (as in Lab), opposed to a pseudo magenta / green axis,
• or, if you have temperature on one axis, you have: one pseudo blue (blue mixed with cyan, so azure?) / amber (red mixed with yellow) axis and, this time, to keep it orthogonal, a true magenta / green axis.

As long as they’re designed this way, you’re fine when it comes to being able to adjust colour individually.

@rom9

What if i let the user pick two spots, not neutral gray but two spots of any color, and then adjust those colors so that they resemble the real colors in the original scene?

gee, I was brushing my teeth and I was thinking about spots, too xD but not exactly in the same way.
Honestly, I don’t know, in advance, how it’s going to feel, especially with white balance thrown in the middle. How repeatable is it going to be, from frame to frame? Not sure. I can’t tell before trying it out. I have the same concerns as @nicnilov, when it comes to UX

I thought: what if you have some sort of multi-spot tool (make it resizable, too, right ? ) for these exponents?

• current behaviour: user picks two spots, and it’s in their interest that they be as far apart as possible to best approximate the exponentiation curve.
• suggested idea: user picks more two neutral spots or more (maybe up to 9 or 10 ?) and clicks a button to finish the sampling. This way, instead of having only two dots as material to estimate the curve, you have more samples. I know it adds challenges, when it comes to managing outliers but I thought I’d pitch this

@nicnilov

The scenes I mentioned before may well contain neutral gray spots, but they lit by colored light, so nothing in the scene is neutral anymore. The difficult thing is to reproduce the color of that light.

@nicnilov, I hear you! that’s actually why I’ve been back to WB basics: sometimes, an image is just completely off and, by eye, I don’t know where to start so I’m very happy if I’m given a tool such as an autoWB (auto rgb grey, or something more elaborate, such as the “auto iterate temperature correlation”) or a spot WB for those lucky frames containing a neutral object. At least, it gives a reasonably better place to start. Then, with Temperature and Tint sliders, I know how to move towards the desired look (hello amber sunset shots with absolutely no grey whatsoever).

(oh and it’s time we threw in our special negatives here! you know, those on daylight film, shot with FL-D, FL-W, or with temperature conversion 80/85 filters)

note: I’m mentioning this “auto iterate temperature correlation” as it’s, at least on paper, an interesting feature, that aims at taking into account the overall shift in colour balance, provided lighting has a sufficiently broad spectrum (i.e. forget about using this feature for fluo shots).

additional note: it’s going to be an off-topic conversation if we stray towards WB considerations This makes me think of Apple Aperture (probably present in Apple Photos too?) WB tool: you can either target natural grey (and deviate from it with a temperature slider) or target skin tones (and also deviate from them with a slider). I thought I’d share it here, as I guess only “few” people know about this neat feature (which is now probably embedded in Apple’s apps).