Teach Yourself Adobe Photoshop CS2.pdf - Online Public Access ...

This document was created by an unregistered ChmMagic, please go to http://www.bisenter.com to register it. Thankssaves files in the least possible amount of disk space. One point to remember is that if you save a JPEG image a second time as a JPEG,it is compressed again and loses more information. If you work on a JPEG file a lot, you can end up with an unreadable picture. If you'regoing to work on a picture, save it as a Photoshop file. Don't make it a JPEG until you're done with it and ready to post it on your Webpage. If you have to change the image, trash the JPEG file and go back to the Photoshop version.When you have files you want to save for future reference, you can save them in the normal way as Photoshop documents (with a .psdfilename extension) or in whatever format you prefer to work in, and then compress the files with a utility such as StuffIt or PKZip orWinZip. All these file compression utilities use lossless compression algorithms and shrink your image files by anywhere from 20% to 50%.That said, compressing JPEG or GIF files is relatively useless because they're already compressed. You won't gain more than a fewpercent of additional compression.Figure 2.6 shows a typical digital photograph that I saved in a number of different file types. (The original is about 5 inches wide, andsaved at 200 dpi.) Table 2.1 shows the more common file types and the sizes of the files that this picture required. The version shown is aPSD, the native Photoshop format.Table 2.1. File Format/File Size Comparisons for Figure 2.6FormatPhotoshop nativeBMPEPSGIFJPEG (high quality)JPEG (low quality)PDF (medium quality)PNG (interlaced)TIFF (LZW compression)File Size1.97MB1.97MB2.82MB536KB272KB192KB188KB1.3MB1.4MBFigure 2.6. If storage space isn't a problem, don't compress the picture.