What is your L*AB adjustments workflow/philosophy in RT?

I have been aware of the CIELAB color space (color model?–these terms seem to be thrown around imprecisely) for years, but never bothered to learn much about it as a LR user. However, I just watched Andy Astbury’s video on L*AB and am now convinced that this adjustments panel is well worth the effort to learn in RT.

For me personally, I think this is one good consequence of my ditching LR and PS (I detest the “software as a service” model)–specifically that I am progressing beyond my somewhat lazy, ingrained habits in raw development. (I am a scientist and cannot devote full-time effort to my photography hobby).

However, transitioning from RGB color space–and the easy habits of tweaking vibrance, exposure, white balance, and clarity in LR–to the curves and equalizer-based adjustments in the LAB panel has been challenging. Some effort, experience, and tweaking will undoubtedly be necessary to master the various adjustments (LH, CH, CC, etc.). Nevertheless, I am getting some decent results on many photos. However, there are a few instances/photos in which I simply cannot duplicate some of the results I liked from LR. (and this involves more than just hue, contrast, but also sharpening… a topic for another thread)

My questions are:

How many of you use LAB and how do you combine it with other adjustments?

Where do the LAB adjustments fit into your workflow?

If you use the L-channel curve to adjust tone and contrast, do you then avoid using any of the exposure sliders, and curves elsewhere–i.e., under the Exposure tab?

If you adjust hue and saturation–SORRY chrominance! :smiley: – in LAB, do you then avoid doing it elsewhere?

How do LAB adjustments interact with, say, the White Balance tab? Isn’t tweaking with Temperature and Tint sliders in the White Balance panel doing the same thing (but less precisely) than adjusting A and B channel curves in the LAB panel?

What hue, chrominance, tonal, etc adjustments do you use the LAB panel for, and what do you prefer to accomplish elsewhere?

Thanks for your thoughts.

Kevin

Hi @Kadsura, I only use the Lab tools sparingly and actually only to add chrominance, roughly +20 is my default. For my taste it adds just enough color boost to my photo’s. The luminance and contast sliders never seem to work intuitively for me, probably because I don’t consider the color model and its effects properly.

Good questions. I’m no expert but here is my thinking about LAB:
a) It is properly a color model rather than a color space. The space it covers is the full CIE visual color range. The history is a bit complex and the ultimate goal of the system was not quite achieved but basically the idea was that a one unit change in any of Lab for any color should have a comparable effect as for some other color. Also, it divorces luminance completely from color, which helps avoid unwanted color shifts.

b) that avoidance of unexpected color shifts is one of the main reasons for my using Lab (which by the way should properly be written Lab* so as to avoid confusion with some older Lab systems). Sometimes I find it easier to just think in Lab terms.

c) I tend to use Lab for images that “need more work”. For an almost perfectly exposed and lit image the RGB tools are more than adequate. Lab comes into play if more drastic editing is called for.

d) I do mix and match Lab and RGB tools but but only if necessary as the choices of what to alter for what end get very complex.

e) same for chrominance, best used alone in most cases but don’t hesitate to try mixing if it seems necessary.

f) using the White balance can accomplish similar things to Lab but it is easy to overdo things in White Balance. White Balance seeks to keep things related to “true” white as defined by black-body radiation (check out Wikipedia if this is new to you) so it is great if the whites in your image seem tinted. Again, there is no automatic reason to prefer either tool over the other, just whichever accomplishes the goal most easily for you.

g) I often work with the L curve in Lab, rather rarely with the others but they are all very useful for dealing with specific problems.

I’m sure others who have a stronger knowledge of image processing may have other thoughts and I am happy to receive corrections but this is my best set of answers to your questions.

Louis

There has been a recent addition to Rawpedia by @jdc that touches on some of the aspects of Lab, CIECAM and RGB: http://rawpedia.rawtherapee.com/Toolchain_Pipeline#Colorimetry

It’s also worth checking out the Image Adjustments section of the CIECAM 2002 tool in the Advanced tab where you can adjust lightness, brightness, chroma, saturation and colorfulness.

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I hadn’t seen that Rawpedia page yet. Very well put.

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I actually did a video, that shows a little bit how I use it.

Maybe this gives you some ideas.
:smiley:

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Thanks for your replies. I will look at the posted video! Interestingly enough, the other night, I was tweaking a few things in the RGB panel–thinking I was in LAB–and I did notice some fairly obvious hue shifts. After pondering whether i liked the change (I decided I did not), I realized my error and headed over to the LAB panel. Theoretically, I knew that L is totally divorced from A and B in LAB, but seeing these in action on one of my own photos really drove the point home.

These curves and equalizers seem a little easier now, but I will sometimes just try the “tin-pan alley” (Thanks Andy! :slightly_smiling_face: ) solutions of the lightness, chromaticity and contrast sliders. if these give me what i want, then I’m generally not too interested in tweaking further.