What is LAB ?

[Mustafa Umut Sarac]

Is it a part of PS or Plug in or another software ?

Mustafa Umut Sarac
Istanbul

[Ken Lee]

Perform a Google search for "LAB Mode" - there are countless free tutorials and videos :)

[Peter De Smidt]

It is a 3 channel color space. It has an L (luminance), A (green/magenta), and B (blue/yellow) channel.

[John Rodriguez]

http://www.amazon.com/Photoshop-LAB-Color-Adventures-Colorspace/dp/0321356780/ref=sr_1_1?ie=UTF8&qid=1328330596&sr=8-1

Have fun :D

[sanking]

Ask Bob Carnie!!

Sandy King

[akfreak]

A digital subject, something I can add to, yeah! Lab Color Mode (LAB) is an alternative colorspace that enables you to manipulate the luminosity and colour of your images. Lab offers more flexibly and is more powerful than when working within RGB.

The advantages of LAB over RGB its ability to dramatically alter color both in terms of tone and saturation also more flexibly and with less degradation to your images than when using RGB. LAB will dramatically alter the contrast of an image without affecting its colour balance or saturation.

LAB will also you to increase the saturation of an image with less image noise and cleaner colour separation than when working in RGB. Also it lets you alter the tone and color balance of your images by adjusting the ‘a’ and ‘b’ channels within LAB.
Another thing LAB allows you to invert specific colors and colour ranges using the Curves tool within LAB. (curves is great because it doesn't increase the file size much and gives ultimate control if you learn to stack curves in layers).

LAB, is more complex than either RGB or CMYK some things to know. Any digital photograph you open within Photoshop will initially be an RGB image that you will need to convert to LAB before you can use this mode.

There are two ways to do this. First, you can use Photoshop’s "Convert to Profile" in the the edit menu or, more simply, use the Mode command, available from the Image menu (Image → Mode → Lab Color). This conversion can be carried out at any point during post-production. Note, that if you have been working in RGB and have a number of adjustment layers you will need to flatten before you do the conversion. The reason for this is the adjustment layers work differently in RGB than in LAB.

Example, The Curves adjustment layer in RGB is way way different to one in LAB. So any of the changes that it makes to an image must be either put into effect prior to the conversion or discarded, i.e. you can flatten the image with the adjustment layer enabled and the changes it makes to an image will be embedded into the flattened image. Also you can disable the layer prior to flattening it, in that case it will have no effect on the final image.

I always convert to LAB at the start (if I feel LAB is the best mode to use during post-production), then stay in LAB until I’m ready to send the file to a client or output the image for the web. At that point I will convert back to RGB.

Some specifics
The Lightness Curve in LAB alters the luminosity of a given pixel independently of its colour data in much the same way as the RGB Curve in RGB when the blend mode of the Curves adjustment layer is set to luminosity. The only difference you might notice when working with the Lightness Curve is numerical, Example in RGB the points on a Curve are divided in values between 0 and 255 but the Lightness Curve operates on a 0 to 100 scale.

The "a" and "b" channels in LAB are more complex. These two channels carry the colour data for the image and the a channel controls the green and magenta tones of an image and the b channel controls the blue and yellow data.

I could write a book on LAB Color. but I dont have to! If you really want to understand Photoshop LAB Color, get this book (http://www.amazon.com/Photoshop-LAB-Color-Adventures-Colorspace/dp/0321356780); The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace’ by Dan Margulis Edit*** I see John Rodriguez already linked the same book. I guess that says somthing about how good the book is ;)))

[bob carnie]

akfreak is my new hero.

I cannot add much,,,, Lab numbers are more intuitive to someone who is use to colour enlarger printing. Sharpening in the L channel rather than on the colours is the bomb.
The Man from Mars move is great move when wanting to pop dull scenes, or create tonal separation for black and white conversion, L channel is 0-100 with this in mind and a good workflow you can set your aim points for many papers- yes they are all different.

I use LAB for every image in some way.

Disadvantages- Lab is very powerful tool and you must use it wisely grasshoppers, You can easily f...k up the image fast.

Mustafa this may be the tool for you but use it sparingly.

[Mustafa Umut Sarac]

Thank you for your kind answers.
Can LAB mode be an answer to below listed question. Please tell me about it , I asked it starting from APUG to astronomy photography forums but no feedback. It is very critical for me and I believe for others .

http://www.largeformatphotography.info/forum/showthread.php?t=86584

Thank you ,

Mustafa Umut Sarac
Istanbul

[Mustafa Umut Sarac]

http://4.bp.blogspot.com/-I6wawYXB6TY/Ty1NAAp0FaI/AAAAAAAABSw/Um4OOB5tbbI/s400/096%2BAutochrome.jpg

[Peter De Smidt]

We're getting way beyond my pay grade, but it sounds like you might need to make your own Autochrome color space. You might try contacting Joseph Holmes (http://www.josephholmes.com/). He made an Ektachrome space (ektaspace), among a number of others.

[Sevo]

Thank you for your kind answers.
Can LAB mode be an answer to below listed question.

"Below listed question" being "can I use another colour space to simulate Lumiere Autochrome". That hasn't really anything to do with Lab or other editing colour spaces - for any sane and stable workflow you'd have to adjust the output colour space to your needs, i.e. calibrate all the displays and printers used to Autochrome standards (i.e. RGB with rather peculiar dyes and a high margin for error).

If you want to/have to fake it at the edit stage - as you'll have to do if you want to use a print shop who does not oblige you with a custom output colour space - I suppose using RGB would be less of a hassle, as Lab (or CMYK) would add yet another layer of complexity. But I might be wrong - I haven't ever tried it...

[Mustafa Umut Sarac]

Thank you Peter ,

I did , Its a very complicated process.

Umut

[Mustafa Umut Sarac]

Thank you Sevo.

I did contacted with an expert who profits from his work.
I will report the results and by the way if anyone may want to comment , please do it.

Thank you ,

Umut

[akfreak]

to make a color space you will need to have some sort of target made and profiled. Then you can create a custom profile for your monitor to work in that space. The key is you have an exact refrence to work from, like an IT8 target and the supporting calibated file.