Request: LAB readout


I come from using Adobe and Capture One and I have always used LAB readouts (Lightroom Classic) and in Capture One for correcting colors by the numbers.

I wish we could get this option in PhotoLab too so that it is easier to correct by A and B values. This is something that I consider as a dealbreaker on a long term because I have used that for so many year and really like using it. I also know other professionals missing LAB readouts, so there is potential for more customers down the road.

Thanks for your attention


Could you elaborate, please Aleksander … What’s a LAB readout - and how is it used ?

Hi @John-M !

PhotoLab and most other software have RGB value readout, to tell what the pixels beneath mouse pointer consist of (in RGB values, ex 128,128,128), usually close to where histogram is located.

Some others gives you ability to select percent of RGB or CMYK (Lightroom and Photoshop), and some others have even more options (Capture One).

These tools are used to measure and verify readout values for people who need to know what their reds really is, ex in product photography. Some others like me use it to verify colors/hues of their landscapes and occasionally peoples skin, to make sure the colors are pretty close to what is the relative industry standard for the subject we are shooting and editing.

Some say you can do it easily with RGB and CMYK, but those are bound to a profile (AdobeRGB, sRGB, MelissaRGB, CMYK US Swop, CMYK EU pre-press, etc), so the numbers won’t be the same depending on the simulated medium you are targeting or the colorspace you edit in.

LAB is LAB, and LAB don’t have this problem. When you set LAB readout in Photoshop or Lightroom, you know that reds in your X image should be exactly same as the red in Y image using A and B channels. This is also easier than using three 255 datapoint channels like RGB, because LAB is -100 to +100 in all channels, and 0 in A and B is neutral. So making a certain shade neutral is no problem, and the colors you need to match is separated from the Lightness channel, so you are only evaluating the hues.

There is a lot of industry standard cheatsheets to measure and correct by. Some are made by Dan Margulis (known as the GURU of LAB). I’ll attach them to this reply if possible.

DXO PhotoLab really needs LAB readout. It is almost the only serious editing software that doesn’t give us this function, and it is limiting their customer base to those who really don’t need or know about it. But there is so many other people that actually use LAB readouts, professionals that color match is almost always using LAB.

Thanks for replying.


Samples taken from Dan Margulis tool by Julia A.

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Samples taken from Dan Margulis tool by Julia A.

Hello John,

while PhotoLab is primarily a raw file developer, LAB mode is very helpful for customizing RGB files. It allows things that are not possible (or not as easy) in RGB mode.

In RGB mode you have the red, green and blue channel – each of them containing the values for Lightness and Colour combined.

In LAB mode you have separated Lightness from Colour, which is
L = lightness (0 to 100)
a = green (-) to red (+)
b = blue (-) to yellow (+)

some eamples
Lightness – for adjusting the black and white point as well the contrast without altering the colour values, influencing the sharpness (texture) of the lightness information etc.

a + b channels – for adjusting the colour independent from the overall lightness and contrast, influencing the softness (texture) of the colour information etc.

While searching the Internet, I came across some videos by Chris Swift, intended to explain / demonstrate in a somewhat reduced form (but in theory and practice) what LAB, for example, can be useful for.

Maybe in the future we’ll get an additional LAB mode to make PhotoLab a more comprehensive development tool.


had written the above in the meantime, when I noticed your explanation – still adding it here. :slight_smile:




Supporting lab color schemes would be a great (and necessary) first step in introducing support for raw stills from Blackmagic cameras.

Hi @Wolfgang !

Thank you for also filling in, much appreciated :slightly_smiling_face:

Dan Margulis over at LEDET and Modern Color Theory is also a great resource, he wrote 4-5 books about LAB, then he also made some videos over at those popular photoshop training sites. Still much valued today.

Anyway, I have to make you notice this requirement from my fellow colleagues and others in the industry that this is needed so that we can do colors by the numbers easily. They all like the app and what it brings otherwise. I think you have a great potential here to get more sales when adding this simple readout (simple, as if I know :smile:). I also think it would benefit all users to have option to make a readout stick on screen on a certain point while editing - dynamically changing as you change the curve or controls, but that’s another tool. This one will simply bring in more customers first day it’s added and I could potentially release myself from Adobes claws :slight_smile:

Thank you for considering, and I’m thankful for this great app. I use it daily on my personal stuff.


CIE Lab is not as useful ( except the legacy “margulis” crowd coming from prehistoric age of post-processing ) as color spaces where hue is separated from saturation ( Lch for example ), but of course better than RGB - now the matter is that you also want some controls along with the readout too …

As for readout you can try to use 3rd party apps that grab your monitor RGB numbers ( granted this is not ideal and not 100% precise ) and display it as CIE Lab value ( or other coordinates ) , on Windows for example PowerToys is OK to display HSB coordinates of your RGB color space ( illustrating how PowerToys displays correct HSB coordinates in PS with PS own color readout nearby)

unfortunately it seems PowerToys can’t deal properly convert to CIE Lab , but if you are OK to operate in other paradigm it can help

thinking that “professionals” will come to a converter just for “readout” w/o any other tools to operate in that colorspace is a pipe dream … even RGB curve tool in DxO PL is so painful to use ( starting from the size of the control with no option to get it bigger , through no direct numerical controls for points on the curve except the endpoints , to no presets for curves available just in the tool like in all other proper converters and all the way down to no Lab curves too :smile: )

Just a quick reply. In my case all the editing tools I use supports LAB out of the box, Capture One, Lightroom Classic, Photoshop etc. Not the same case with HSB and HSL AFAIK. I also don’t think those Microsoft tools can be used on Mac either. Everywhere I meet other professionals I see them use LAB too, and it is not just Margulis crowd but people in general. He did contribute a lot, so it is why I mentioned him.

Haven’t had any problems using the built-in color picker in the OS or programs, but when I used Windows workstation, it was a different story. Half of the OS use WCS as long as it is supported, rest of the applications must point to the profile in color profile selector. It’s a different story on MAC since all of viewport is forced through the profile from the get-go.

Good old Windows issue where imprecision happens: You calibrated monitor using X-Rite or DisplayCAL or whatever. You think color is the same everywhere like it is on a MAC, wrong. Photoviewer, Lightroom and XnViewer might have 3 different renditions even if 2 of them points to same profile. Fun case, old Photo Viewer is color managed, new Photos on Windows isn’t! But this is a Windows topic and not a MAC topic. The inaccuracy is mostly because you are unable to point mouse to same exact place twice. The better option is to have a static point like you show in PS.

Nah, I know a few. Mileage may vary. You don’t need to know point in curve if you have a readout position. The curve number isn’t as important as the readout point.

Anyway, great insights!

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PS for example has HSB readouts out of the box … but HSB (HSL, HSV) is not a color space of course, it is just different system coordinates for some RGB color space

delusion of grandeur detected …

that depends on who are “you” and what tools “you” are using, proper tool will let one to navigate to the exactly the same pixel … inprecision that I was referring to has to do with the math and that picking RGB data from display driver when working with 15/16 bit or floating point coordinates in the actual image data are not precise but shall be OK for somebody who , for example, tries to adjust K/tint sliders navigating to some vicinity of desired skin tone by “numbers”

On Mac, you have the “Digital Colour Meter” Tool that supports LAB space and various sampling sizes:

Yes, PS probably have HSB, but in reality, if you compare all the apps that is available, even OpenSource ones like Darktable, RAWTherapee, etc, you find that LAB is universally used while HSB is not. Yes we can agree on that it is not a colorspace :smiley:

delusion of grandeur detected …

That was non-intentional, it may be limitation of my poor English as it is not even my 2nd language. But it is what it is. If I go to our newspaper, what do you think they use of color matching? CMYK, LAB, RGB or HSB. RGB and LAB side by side most of the time, although for accuracy they know that RGB depends on colorspace too.

that depends on who are “you” and what tools “you” are using, proper tool will let one to navigate to the exactly the same pixel

So on a 4k monitor with maybe a software grid size of 9x9px measuring point, do you think you are able to hit that exact same point? I doubt it, but also not impossible. I’m just saying, that could be a factor. I do think it is better putting down locked points in the image documents that gives a dynamically read-out whenever things change. If the measuring point never move, it is up to the sliders to get where they need to be. I rarely try to be that spesific though, “close to specs” is good enough for me with what I do. I do however feel it is way easier to interpret colors by looking at A and B rather than RGB values and HSB, it is ingrained in my memory, negative is green and blue, positives is magenta and blue. Takes seconds to evaluate and edit.

I am sorry for my poor English if I don’t make myself understood or if things are read the wrong way. I try to keep polite and as little D-head as possible :smiley:

I will have to check back way later in this thread. During this text I got a notice that someone is going to pass away in close family, in any moment now, so I hope you don’t think I left for no reason after this reply. Not that it matter anyway, but it is said. I will read later though. Thanks for insights and the productive discussions :slight_smile: :pray:


Yes, I see now. But this is impossible to place in relative same position as you edit, no?

Well, it is a small fix at the moment if it is possible to have “always on top”.

Great tip :fist_left:t2:

Actually, you can do that, look at the View options,

you can fix the coordinate of your mouse position (just press Command + L), and when you set the option to “Update continuously”, it will update the value when you change the sliders.

The only problem is how to keep the window always on top. You might have to keep it in a window next to Photolab. I believe there are also third-party apps that add the always-on-top functionality, but I have never tried any.

Way back when I did art direction and ran pixel editors, LAB was very useful to sharpen images by transforming into LAB from RGB and then apply low number of unsharp masks twice in the Luminance channel only.
And then go back into RGB.

But sharpening and noise management are way past that nowadays. :slight_smile:

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Au contraire; your English is excellent - - I would have never guessed that you were not a native English speaker (writer) … AND, I’m equally impressed with your measured response to Mr NoName’s attempt at provocation !

  • His approach is puzzling; he’s obviously very well informed on many photography/colour topics - but, then he veers off into troll-like responses … and it’s worrying (to me, at least) that he’s not prepared to explain/reveal a little about himself.