Lab Color is a colour mode that is not unique to Photoshop. Like other colour modes that you may be more familiar with such as RGB and CMYK, Lab Color is a global colour model where you can specify any given colour by giving numeric values across different channels.
A few facts about Lab Color:
• Lab Color is used for many things outside the realms of photography, digital & print to specify colours because of its accuracy.
• It is used widely across industries such as the automotive industry, the textile industry and more because it has a wider colour gamut than RGB and CMYK.
• Lab Color is used as the global colour mode, which can be matched against all the rest; A business which needs to match their brand colour in print, digital, textile, paint colour etc could use lab colour values to make sure their brand colour was the same across multiple the applications.
• Unlike the other colour modes there is no output from Lab Color, whatever the item it would need to be changed into a different colour mode for output – such as CMYK if it were to be printed.
How it works:
Most of our colour modes are based on how much of a certain colour is needed to be displayed for a certain device. For example RGB is how much Red, Green and Blue needs to be displayed to show the correct colour on a digital screen and CMYK values are for how much colour is needed for a 4 colour print. The LAB colour model is based on how humans see colour; How much colour there is on the green to red axis combined with how much colour there is on the blue to yellow axis, combined with a lightness value from light to dark. The diagram below shows how this works:
To understand the colour theory more, it will help to change one of your own images to Lab colour. I have chosen to use an image of Blueberries. If you want to use the same image you can get it here.
There are 2 ways to change your image to Lab colour in Photoshop:
You can choose Image > Mode > Lab Color
or go to Edit > Convert to Profile > Lab Color.
When looking at a image in LAB colour mode in Photoshop you will see these 3 models working together in the Channels palette. The top channel Lab shows all channels working together and below where it is split into the other 3 channels of Lightness, Channel A & Channel B.
To open the channels palette go to: Windows > Channels.
By turning off the visibility (eye icon) next to the channels you will be able to see each channel as a larger view on the canvas.
The Lightness Channel (shown below) holds all the information for how light or dark the image is, so just the lightness and no colour information at all. Looking at just this channel is very much like looking at the grayscale version of an image going from values of 0 which is black and 100 white.
Channel A holds colour information on a scale from green to red.
Channel B holds information on a scale that goes from blue to yellow.
The cross over colour on each of the 3 channels will be a neutral grey that contains equal amounts of each in the middle of the sphere.
Why would you choose to edit your images in Lab colour?
The wider gamut of colour in Lab Color means you can enhance colour in photos in a way that you just can’t do in RGB or CMYK.
Coming soon: How to make your colours pop – using Lab Color in Photoshop to add more colour.