via the lens Loc: Northern California, near Yosemite NP

Hi, for anyone who knows about LAB color values instead of RGB color values, please provide insight. I have no experience with LAB values. Yes, I can do a search on this and did, see below, but would like input from people who know and have used LAB and why they use or would use it. I can view the image in LR with LAB colors but don't know why I would do that or how it might improve an image. I always check the RGB colors if I see any issue with color tones or shadows and highlights. I'm an experienced LR user and photographer so I get all the stuff about histograms, color spaces, etc. and don't need that information. Just curious about LAB values and if anyone might use them in LR and why.

From RawPedia:
RGB and CIE L*a*b* (or just "Lab") are two different color spaces, or ways of describing colors.

Many people wonder what the differences are between adjusting lightness, contrast and saturation in the RGB color space, or lightness, contrast and chromaticity in the Lab color space. RGB operates on three channels: red, green and blue. Lab is a conversion of the same information to a lightness component L*, and two color components - a* and b*. Lightness is kept separate from color, so that you can adjust one without affecting the other. "Lightness" is designed to approximate human vision, which is very sensitive to green but less to blue. If you brighten in Lab space, the result will often look more correct to the eye, color-wise. In general we can say that when using positive values for the saturation slider in Lab space, the colors come out more 'fresh', while using the same amount of saturation in RGB makes colors look 'warmer'.

johngault007 Loc: Florida Panhandle

I use LAB on pretty much every RAW file I process. I don't use it in Lightroom, so your mileage may vary on the following:

For me it is available in pretty much any module in the Tone Group of Darktable. My main usage is in the Tone Curve module and selecting LAB (independent channels) allows me to break luminance (l-channel) and chrominance (a/b channels) apart.
Example: If I decide I need to tweak highlights, midtones, and shadows without changing the color saturation for each pixel, this would be the perfect reason to do so.

Here's a quick excerpt from the DT user manual that explains is a little differently:

Lab is a perceptual color space that is designed to approximate the way human beings
perceive colors and lightness, and representing the color information independently of
the the lightness information. In “Lab, separated channels”, you get a fully independent
control over the chrominance (a/b-channels) and the luminance (L-channel). In “Lab,
linked channels”, only the luminance (L-channel) control is available. The color saturation
correction will be automatically computed, for each pixel, from the contrast correction
applied to the luminance channel. This works better in cases where a subtle contrast
correction is applied, but gives increasingly inaccurate saturation correction as the
contrast gets more dramatically enhanced.

via the lens Loc: Northern California, near Yosemite NP

Thanks, I'll have to read that a couple of times. Are you able to discern a difference in the same RAW edited file using LAB versus RGB for correction?

johngault007 Loc: Florida Panhandle

I may be completely off base here, but using LAB vs. RGB is on the input side so you are basically modifying the file at the pixel level with no effect on the output.

As long as I'm not making drastic changes to the luminance channel, there is a big difference for me compared to RGB. It provides finer control for each channel for small modifications.

Ysarex Loc: St. Louis

In LR the Lab values are strictly informational. You can't edit the image in the Lab space from within LR. Other editors can but it's fairly obscure. RawTherapee and DarkTable have the option to apply Lab edits and of course Photoshop -- more common in raster editors.

It can be handy. When you apply RGB edits that alter tone you're going to also get changes in color saturation. The Lab model lets you address tone and saturation separately. It's not a huge deal because most RGB editors provide appropriate tools Like LR's HSL adjustment that will usually get the need job done.

Joe

via the lens Loc: Northern California, near Yosemite NP

Thanks to you both! Good information to know. I'll have to play around a bit with PS to understand the benefit of using LAB.

JohnCl Loc: Central Arizona

I have found Dan Margulis' book "Photoshop LAB Color" to be an excellent source.

JohnCl Loc: Central Arizona

I have found Dan Margulis' "Photoshop LAB Color" an excellent source for this.

via the lens Loc: Northern California, near Yosemite NP

Thanks for the tip to a source, I'll look that up.

bleirer

I've followed a couple videos and emulated the things they did, but I'm not fully versed in it. It breaks luminosity out into a separate channel and puts color on two axis' similar to the way white balance and tint are on two axis' in lightroom. So you can open a curves adjustment but control each channels curve independently. I like how you can use the tool to click in the image to affect the color at that point without changing saturation or lightness. There are a lot of good videos. Here are two I liked:

https://petapixel.com/2017/09/14/using-lab-color-photoshop-add-color-punch-images/

https://phlearn.com/tutorial/get-amazing-colors-without-changing-anything-else/

via the lens Loc: Northern California, near Yosemite NP

Thanks!

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

The most comprehensive source for learning how to work with Lab color has to be this book:

https://www.peachpit.com/store/photoshop-lab-color-the-canyon-conundrum-and-other-9780134176109

via the lens Loc: Northern California, near Yosemite NP

Thanks, I'll check it out.

dsmeltz Loc: Philadelphia

So the LAB advantage is making a color change without having to adjust luminescence or contrast or some other linked aspect afterward? So if LAB was easily convertible to other output, it could improve workflow?

johngault007 Loc: Florida Panhandle

It does for me

It's built directly into the workflow of my editor. If I don't need it, I just bypass it, or go back to it later if something is a bit off.