LAB Colour Space

[Abitconfused]

Does anyone convert to LAB Colour Space to adjust A and B channels?

[Manfred M]

So far as I remember, I've only ever worked with the L channel.

[James G]

Probably about 5years back, and mostly if memory serves when I was working on astrophotography. Like Manfred I more usually worked the L channel.

I can't think of the last time I switched into Lab mode.

[DanK]

I have a few times, but I don't bother any more. The real benefit, IMHO, is the ability to separate luminance from everything else. I find that valuable. For example, a simple tone-curve adjustment to increase contrast will increase saturation as well, which I often don't want. (It's particularly undesirable with flower images with highly a highly saturated color.) However, in my opinion, the simplest way to deal with this is to change the blend mode of the adjustment layer to luminance.

[xpatUSA]

Does anyone convert to LAB Colour Space to adjust A and B channels?

I use it often for Lightness, Contrast and Chromaticity adjustments but not a* or b* until just now, voila:



I played with the "A channel" (a*) just to see what it did. I found that, by "reddening up" the curve shown, it richened the wood color quite nicely - it looked more like plain yellow pine before.

The main difficulty I see is in envisaging the effect of the adjustment in an image with a specific need, rather than just bringing up any old image and playing, like I did here. Should be plenty of tutorials/articles out there, I imagine.

[Manfred M]

The definitive book on using the LAB colour space is Dan Margulis Photoshop LAB Color: The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace The second edition came out late last year.

It's only available in book form, so fare as I know and it is not cheap.

https://www.amazon.com/Photoshop-LAB...V2936RT95NJ2ZR

[proseak]

Rarely - it can be useful as a way of changing saturation; steepening "A" increases saturation in magenta/green, steepening "B" increases saturation in blue/yellow. It does this throughout the luminance range.

Dan Margulis is worth checking out; as well as the book mentioned by Manfred there are videos available on Youtube

[escaladieu]

Yes, I do sometimes. Adding contrast to the A & B will boost colour intensity & seperation. Its useful for some, but not all images. Dan's book on LAB covers it all.

[dennybeall]

Just have used Luminance channel but not others.

[Cantab]

The definitive book on using the LAB colour space is Dan Margulis Photoshop LAB Color: The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace The second edition came out late last year.

It's only available in book form, so fare as I know and it is not cheap.

https://www.amazon.com/Photoshop-LAB...V2936RT95NJ2ZR

Manfred, apart from its being the definitive book, have you found it useful in actual practice? I read the blurb on the Amazon website; the book looks interesting. I checked several other online book sellers; their prices are all remarkedly similar.

[Manfred M]

Manfred, apart from its being the definitive book, have you found it useful in actual practice? I read the blurb on the Amazon website; the book looks interesting. I checked several other online book sellers; their prices are all remarkedly similar.

I've started to read it, but haven't gotten all that far. This is generally not the time of year I spend curled up with photography books - too much else to do!

[Shadowman]

Ed,

Is L*a*b* something you just want to experiment with or do you have limited access to other color spaces? I'd love to use cmyk but don't use Photoshop, Elements and Lightroom are limited to rgb, supposedly Gimp uses cmyk but I haven't been able to access the plugin. I became a bit obsessed with cmyk as it is often used to adjust skintones, however most available programs have workarounds and presets that give you good methods for alerting the colors you've captured.

[xpatUSA]

. . .I'd love to use cmyk but don't use Photoshop, Elements and Lightroom are limited to rgb, supposedly Gimp uses cmyk but I haven't been able to access the plugin.

I guess you've tried Colors > Components > Decompose and then selected CMYK from the drop-down?

I seem to to recall that I had to add something to get 'decompose' though, I'll take look . . .

. . . well, according the manual you should be able to get CMYK split into layers - see section 8.16 - and then be able recombine the layers with 'Recompose'.

I may have misunderstood you. My version is 2.8.16 if that's of any help . . .

[Shadowman]

I guess you've tried Colors > Components > Decompose and then selected CMYK from the drop-down?

I seem to to recall that I had to add something to get 'decompose' though, I'll take look . . .

. . . well, according the manual you should be able to get CMYK split into layers - see section 8.16 - and then be able recombine the layers with 'Recompose'.

I may have misunderstood you. My version is 2.8.16 if that's of any help . . .

It's there, thanks.