It's time to start thinking about the output of our image - whether we'd like it to be printed or just display it on the web. The two main concerns we have when thinking about output are the resolution and the file type. What you intend to use your image for will affect both the image's resolution and what type of file it's saved as.
Let's start by learning more about image resolution.
Understanding image resolution
Digital images are made up of rows of tiny square-shaped spots of color called pixels. If we zoom in far enough on an image, Photoshop will display the individual pixels of color like we see in the following close-up image of the girl's shovel:
When these pixels are printed, they are translated into dots of ink on the page. Resolution refers to the number of these dots that are displayed per linear unit of surface. Units of resolution are typically represented in pixels per inch (ppi) on a monitor, or dots per inch (dpi) on a printed surface. When there are more of these dots per color per linear unit, our eyes can’t pick out the individual spots of color and they appear to mingle into smooth, continuous tones. The higher the resolution, or number of dots per unit of surface, the smoother our image will look. However, if we have too low of a resolution, an image may end up looking grainy or blurry.
When creating an image, or preparing it for use outside of Photoshop, you’ll want to think about the intended destination and set the resolution accordingly. Following are some recommendations for what resolution your images should be:
Printed output: The recommended resolution depends on our destination. Generally, pictures destined to be published on plain paper such as a newsletter may be saved at 150-200 dpi. For printing photos on a specialized photo printer, the minimum recommended resolution is 240. However, 300 dpi is best if we are printing out on high-quality photo paper. Remember, we can't print out an image any better than the limitations of our printer. For best results, we should check our printer's recommendations.
Onscreen display: If using an image on the Web, we'll want to keep the file size relatively small. This reduces the amount of time the user will have to wait to view the image. For images intended for PowerPoint presentations or Web pages, we should use an image resolution of 72 dpi.
Let's look at our image’s pixel resolution now. We can do this in the Image Size dialog box.