Adobe 65023809 Printing Guide - Page 58

Multiple layers can be used for complex compositing and color correction; type and other vector components can add to visual interest, and consistent color management across Creative Suite 4 ensures predictable output. General Guidelines While your workflow has its own particular requirements, some general rules about resolution and color space still apply. When you supply specifications to your customers, to help them prepare jobs for submission, it's important to make sure that they're educated about issues you encounter with image content. The increasing use of digital cameras means that many designers are submitting their own images, rather than relying on professional scanner operators to handle the scaling, color, retouching, and resolution control that previously was the province of print service providers or color trade shops. This section will help you educate customers, as well as provide guidance for handling customer images that need modification to solve printing problems. Resolution Whether its origin is a digital camera or scanner, an image is composed of pixels (short for "picture element"). The number of these little colored squares per linear inch (or per centimeter, depending on your system of measurement) is described as the resolution of the image, expressed in pixels per inch (ppi). The higher the resolution of an image that's a given size, the more detail that can be displayed. 36 ppi: 128 KB 72 ppi: 236 KB 300 ppi: 2.2 MB Image Resolution The higher the number of the pixels per inch (ppi), the more detail an image can display. More pixels per inch also means larger image size. Increasing the resolution, or upsampling, from 72 ppi to 300 ppi in Photoshop does not recreate missing information. Note the softening of detail in the image that has been upsampled in Photoshop, compared to an image scanned to the correct size at the 300-ppi resolution. Upsampling: Resolution increased to 300 ppi from 72 ppi. The appropriate resolution for an image to be printed, based on the final line screen, is 1.5 to 2 times the line screen, at or above its final size. For example, an image to be printed at 150 lines per inch (lpi) should be scanned to final size with a resolution of 225 ppi to 300 ppi. There is no advantage to exceeding 300 ppi for an image to be printed at 150 lpi; the excess information incurs unnecessary processing with no visual improvement. Rather than do the math, most users elect to use 300 ppi as a general target resolution. It's important to emphasize that, whatever the target resolution, the image must be scanned (or photographed digitally) at or above its final printing size. That is, an image intended to print at a size of 5 x 7 inches and a line screen of 150 lpi should be scanned to 5 x 7 inches at 300 ppi. Scanning an image at 300 ppi, but at a size of 2 x 3 inches, with the intention of scaling up the image to the correct final size of 5 x 7 inches (either in Photoshop or in a page layout program), will compromise detail after resizing. Photoshop can interpolate information, but this results in Adobe Creative Suite 4 Printing Guide 56