Using Adobe Photoshop CS, Part 1 - Creating a New File (Page 3 of 15 ) To start from scratch and create a new file, choose File, New or press (Command-N) [Ctrl+N] to access the New dialog box (see Figure 5.12). Here you can give your file a name (you can do this later when you actually save the file too) and choose a size and resolution for your file. Adobe has also included many preset canvas sizes, and you can choose one of those (for example, a 5x7-inch file). Choosing a resolution is very important when you create a Photoshop file because changing the resolution in the file later may cause degradation or distortion in your file. 
Figure 5.11 The File Browser adjusted for a larger preview. 
Figure 5.12 The New document dialog box.
Tip -You can also create your own New document presets by choosing the options you want, and then clicking on the Save Preset button.
There's an option to choose what the default background of your file will be (White, Background Color, or Transparent), and you can click on the Advanced button to choose a color profile or to specify a non-square pixel aspect ratio for video content (see Figure 5.13). 
Figure 5.13 Choosing a video setting from the Advanced section of the New dialog. Color Modes Photoshop lets you create files using any of several color modes, and it's important to know which one to choose. Although you can change color modes later in the process, just about any such change will cause color shifts. Each color mode has agamut, or range of colors that can be produced. Some gamuts are wider, or can contain more colors, than others. For example, there are certain colors that can be displayed in RGB that simply can't be reproduced in CMYK (for example, bright greens or oranges or pastel colors). So converting an RGB file to CMYK might cause some colors to become dull or change color altogether because those colors don't exist in CMYK. Let's take a look at each of the supported color models: Bitmap-Also called 1-bit, a one-bit bitmap image can contain only two colors, black and white (like my favorite kind of cookie). It's useful for certain workflows, such as screen printing or specialized newspaper techniques. Some other programs (Illustrator, for example) can change the black color of a bitmap to a different color, so scanned logos are also sometimes saved as bitmap images. Some cell-phone displays or PDAs also require bitmap images. Grayscale-The Grayscale color model is black and white with a touch of gray-256 levels of gray, that is. Mainly used for single-color artwork such as black-and-white photographs, the Grayscale model is also used to create monotones, duotones, tritones, and quadtones-all of which we'll cover later in the chapter. RGB Color-RGB (Red Green Blue) is asubtractivecolor method. Subtractive means that if you mix all the colors together, the result is white, and if none of the colors are present, the result is black. Televisions, computer monitors, and the like use the RGB color model (when your TV is turned off, the screen is black). When you're working on files that will be used in video, for broadcast, on the Web, or for onscreen presentations, RGB is the format you should use. CMYK Color-Unlike RGB, CMYK is an additive color method, which means that if you mix all the colors together, you get black, but if none of the colors are present, you get white. Anything you see in print uses CMYK (a blank piece of paper is white), so obviously when you're designing content that will be printed in color, CMYK is the color model of choice. CMYK stands for Cyan (a shade of blue), Magenta (a shade of red), Yellow, and Key (Black). Black is referred to as Key because that is traditionally the key color; it reinforces and invigorates the other colors (or so a printer once told me).
Note -As I mentioned earlier, the CMYK gamut isn't anywhere near as wide as most designers would like, so designers use spot colors (for example, Pantone colors) that allow designers to pick a specific color ink (including metallic inks, pastels, and the like).
Lab Color-Almost scientific in nature (as if the other color models weren't), the Lab color model contains a Luminance level called "L" and two channels of color, called "a" and "b" (hence the name Lab). Lab has the widest color gamut of all those listed here, and Photoshop uses this model internally to calculate operations. For example, when you convert an image from RGB to CMYK, Photoshop first internally converts the RGB data to Lab and then converts the Lab data to CMYK. Because very few-if any-applications can use or understand Lab files, I would suggest that you choose this color model only if your image isn't going to be placed into other applications or printed on a press.
 This chapter is from Adobe Creative Suite, by Mordy Golding (Sams, 2003, ISBN: 0672325918). Check it out at your favorite bookstore today. Buy this book now.
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