What About Color Modes ?

Color Modes

For most images, it makes sense to work in RGB color mode until you prepare to print. Then, if you’re printing professionally, convert to CMYK color mode. Let’s take a look at color modes. The color mode (Grayscale, RGB, CMYK, Lab, and so on) determines how many colors—and which colors—you can use in an image. It also determines how many color channels are available. Additionally, the bit depth determines how many colors are available on each channel. A broader range of colrs and a larger number of color channels give you more colors to choose from in your image, but they also increase file size.

    When yo first open an image in Photoshop, is clor mode usually either RGB or Grayscale. You can easily see its color mode and bit dept in the document title bar. The color mode and bit depth (in bits per channel) are in parentheses.

     The most common color modes in Photoshop are Grayscale, RGB, CMYK, and Lab, but you may have use for others occasionally, too. Briefly, the following are the color modes you may need to use in Photoshop:

Bitmap:

    Don’t confuse the Bitmap color mode with the definition of bitmap earlier in this chapter. A bitmap image, composed of pixels, can be in any color mode. But the Bitmap color mode has black pixels
and white pixels, with no shades of gray and no other colors.
Grayscale: 

   When we talk about black-and-white images, we’re usuallyactually referring to grayscale images. In the Grayscale color mode,an image contains black pixels, white pixels, and 254 shades of gray
in between.
Duotone:

   Duotone images are kind of artsy and can give you an oldtimeyeffect or something much more radical. As the name suggests,a duotone image has two inks. Usually, one of the inks is black. You add another color, and Photoshop blends the two. Confusingly, the Duotone color mode is also used for monotones (one ink), tritones (three inks), and quadtones (four inks).
Indexed Color: 

   This color mode is designed to keep your file size small, but it can limit you creatively. With the Indexed Color mode, your image is restricted to a color palette you define. Indexed Color can work okay for images destined for the Web, but if you’ll be printing, you’re usually better off using a different color mode.
RGB Color: 

   Most digital images are in RGB Color mode. RGB stands for red, green, and blue, the additive colors that are displayed on computer monitors and televisions. Additionally, many desktop printers use RGB inks. It’s usually best to work in RGB until you have to convert to a different image mode, because RGB provides a wide range of colors.
CMYK Color: 

   Most printed work, especially professionally printed output, is produced with CMYK (cyan, magenta, yellow, and black) inks. Because the range of colors produced by CMYK differs from that produced by RGB, you should typically convert the image to CMYK Color mode before printing professionally.

Lab Color: 

   Some photographers prefer to work in Lab Color mode, because it includes all the colors you can create in both RGB and CMYK modes. It’s composed of three color channels: Lightness (also known as luminance), a (colors ranging from green to red), and b (colors ranging from blue to yellow). Lab colors are device independent, so they remain consistent on monitors, printers, and scanners. 

Multichannel: 

   This mode is used for specialized printing, so you probably won’t encounter it. In this mode, images contain 256 levels of gray in each channel. When you convert images to Multichannel mode, the original color channels become spot color channels.