The goal of this video is to show the structure of Lab into three-color opponent channels and how this is implemented in Photoshop. Color opponency is explained, as well as the separation of grayscale from color information, and most importantly, how all this is implemented in Photoshop.
- [Instructor] There are three channels in Lab. For comparison, RGB also has three channels and CMYK has four channels. These channels as shown in the diagram are the Lightness or L channel. This channel holds black and white or grayscale information from white to black. The A channel which holds color information from green to magenta. The B channel which holds color information from yellow to blue. While A and B are not as easy to conceptualize in terms of what colors they hold as for example the green channel in RGB, it's apparent that information has been added because each of these channels does double duty and effectively tracks two colors, not just one. The two key properties of LAB that you'll be learning to work with and manipulate in this course can easily be seen in the diagram. They are first the complete separation of black and white information from color information. This will allow you to operate on colors without involving the grayscale aspect of an image which tends to be the structural scaffolding that supports an image. You can also operate only on the monochromatic aspects of an image which means that you can change sharpness and contrast without worrying about making an image muddy or destroying color. Second, it's important to understand that holding two tracks of color information in each channel means that the channel midpoint is neutral in terms of the colors and contains neither color. The midpoint of the L channel is neutral gray. The term for this is color opponent. And as you'll see later in this course, when a channel is opponent, there are tremendous opportunities for creating fun. Understanding has been sometimes called the booby prize and I and probably you are more interested in what you can do with these techniques than the theory that underlies LAB color. Understanding the context of how LAB operates in Photoshop will help, but obviously the rubber meets the road when you start actually doing something with it. So let's move on. There's only one more step before we produce interesting and stunning results, converting from old school RGB and CMYK color spaces to the newfangled, wonderful, altogether marvelous LAB color space. I do also want to mention that there is some confusion about the naming of LAB and its channels. Just like RGB is found written in both all capital letters and in all lowercase letters, you'll find Lab with a capital L at times and in Photoshop the channels are often shown with lowercase letters rather than capitalized at all. Where I get to choose, I will use all capital letters for the LAB channels. But by whatever name, the LAB channels are recognizable and they're completely the same whether the letters are capitalized or in lowercase.
- Converting images to Lab Color space
- Applying Curves to Lab channels
- Selective sharpening
- Inverting channels
- Making per-channel equalizations
- Using the Lab action
- Combining Lab Color with blending modes
- Making patterns with Lab images