Specifying Size and Resolution in Photoshop

Photoshop has evolved into a Swiss Army knife. Once only a pixel-based (or raster) application designed primarily for print, it has been transformed into a program capable of both vector- and pixel-based output with added features aimed at producing Web content as well.

You need to be aware of important issues when you produce both pixel-based and vector-based graphics. I give you a bit of background in that department in this chapter. Also, I show you the components that make up the physical aspect of your pixel-based image — the dimensions, the file size, and the resolution — and how they relate to one another.

Even though Photoshop can now produce vector graphics, its primary mission is to create awe-inspiring raster images. And because the issue of resolution is so critical to raster images, this chapter primarily discusses methods for sizing and resizing raster images.

You find out how to change any of the three components without harming your image. Yes, you can harm your image. Not intentionally, of course. But it can happen quicker than you can close a dialog box. But with a firm understanding of how pixels live and breathe, you can ensure that your images are safe from any undue damage.

Putting Images under the Microscope
Digital images fall into two camps, vector images, which are created based on mathematical formulas, and raster images, which are made up of pixels. Photoshop allows you to produce both types of images and even to combine both types within a single file.