ptg 400 Chapter 16 Reducing the size of a photograph presents its own particular set of problems, and Photoshop comes to the rescue with solutions. For pho- tographic images, the best format to use is the JPEG (Joint Photographic Experts Group) format. This format reduces file size by removing image information (lossy compression). For example, a 1 MB uncompressed TIFF file can be reduced to 20 KB or 30 KB using JPEG compression. That reduces the download time of the image on a 33 KB modem from15 minutes to 10 seconds. While that is quite a reduction, it also means most of the image colors have been removed and the remaining colors are dithered (simulated) to fool the eyes into seeing colors that are no longer in the image. Highly compressed JPEG images look good on a monitor, but fare poorly when sent to a printer. If you’re working with a 16-bit document, you can save it in the JPEG format (8- bit) using the Save As command without having to change the bit depth before hand (New!). Preparing a Photograph for the Web Prepare a Photograph for the Web Open a photographic document. Click the File menu, and then click Save As. Enter a name for the file in the Save As box. Click the Save In (Win) or Where (Mac) list arrow, and then select a location in which to save the file. Click the Format list arrow, and then click JPEG. Click Save. 6 5 4 3 2 1 3 4 5 6 From the Library of Wow! eBook ptg Chapter 16 Controlling Image Output 401 Select from the following JPEG Options: ◆ Matte. The JPEG format does not support transparency. Click the Matte list arrow, and then select the color with which to fill transparent areas within the active document. ◆ Quality. The Quality option determines the amount of image information loss. Enter a value from 1 to 12; the higher the value, the more information is retained, thus creating a larger file. ◆ Baseline (Standard). The format is recognized by most browsers. ◆ Baseline Optimized. Produces optimized color, and a slightly smaller file size, but is not supported by older browsers. ◆ Progressive. Displays a series of increasingly detailed scans as the image downloads. The visual impression is of a blurred image slowly coming into focus (not supported by older browsers). ◆ Scans. If Progressive is selected, select the number of scan passes for the image. Click OK. 8 7 7 8 Using the JPEG 2000 Format JPEG 2000 is a file format that provides more options and greater flexibility than the standard JPEG format. It produces images with better compression and quality for both web and print publishing. The optional JPEG 2000 format plug-in can be found on the Photoshop CS5 installation CD in Goodies/Optional Plug- Ins/Photoshop Only/File Formats. Currently, only computers with the necessary plug-in can view a JPEG 2000 file on the Web. For Your Information From the Library of Wow! eBook ptg 402 Chapter 16 Images saved for press printing are in another world. For example, images displayed on a monitor use the RGB (additive) color space, while images sent to a press use the CMYK (subtractive) color space. The format of choice is the DCS (Desktop Color Separations) format. The DCS format is a version of the standard EPS format that lets you save color separations of CMYK images. DCS comes in two flavors, DCS 1.0 and DCS 2.0. Both create five separate files: one is for each of the four color plates, Cyan, Magenta, Yellow, and Black, and one is for a combined, or composite image. However, the DCS 2.0 format allows you to save alpha and spot-color channels, as well as giving you the option of saving the five separate files under one combined file name. You can also use the DCS 2.0 format to export images containing spot channels. It's important to understand that the only device that can print a DCS file is a PostScript printer. As with anything related to press operations, always contact your friendly press operator and ask what format to use. Preparing an Image for the Press Prepare an Image for the Press Open a document. Click the File menu, and then click Save As. IMPORTANT Images saved in the DCS format must be in the CMYK color mode. Enter a name for the file in the Save As box. Click the Save In (Win) or Where (Mac) list arrow, and then select a location in which to save the file. Click the Format list arrow, and then click Photoshop DCS 2.0. Click Save. 6 5 4 3 2 1 3 4 5 6 From the Library of Wow! eBook ptg Chapter 16 Controlling Image Output 403 Select from the following DCS 2.0 Format options: ◆ Preview. Click the list arrow, and then select what type of low-resolution image to use in the layout application. ◆ DCS. Click the list arrow, and then select how you want the color plate information saved. ◆ Encoding. Click the list arrow, and then select how the image data is encoded for delivery to the output device (contact your service bureau). ◆ Include Halftone Screen. Select the check box to include any halftone screens. ◆ Include Transfer Function. Used with high-end commercial production jobs. ◆ Include Vector Data. Select the check box to include any vector data contained within the active image. ◆ Image Interpolation. Select the check box to create an anti- aliased version of the Preview image (does not impact printing). Click OK. 8 7 7 8 From the Library of Wow! eBook ptg 404 Chapter 16 While not everyone has access to a 4-color press, even casual com- puter users have or have access to, an inkjet or laser printer. Inkjet and laser printers apply color to the paper using dots of ink. In fact, one of the measurements of quality for this type of output is its printing resolu- tion. For example, a photo-quality inkjet or laser printer can have a res- olution of 1,400 dpi and higher, or one thousand four hundred dots of color information per linear inch. There are several file format options to print this type of output; however, none is as versatile as the TIFF for- mat. The Tagged-Image File Format uses lossy or lossless compression, and lets you save multiple Photoshop layers, as well as alpha channel information. In addition, there is hardly a layout application in the mar- ketplace, Macintosh or Windows, that will not open an image saved in the TIFF format. Preparing an Image for an Inkjet or Laser Printer Prepare an Image for an Inkjet or Laser Printer Open a document. Click the File menu, and then click Save As. Enter a name for the file in the Save As box. Click the Save In (Win) or Where (Mac) list arrow, and then select a location in which to save the file. Click the Format list arrow, and then click TIFF. Click Save. 6 5 4 3 2 1 3 4 5 6 From the Library of Wow! eBook ptg Chapter 16 Controlling Image Output 405 Select from the following TIFF Options: ◆ None. No compression is performed to the image. ◆ LZW. Performs lossless compression to the image. When this method is used, the receiving application must have the corresponding LZW option or it will not be able to decompress the file. ◆ Zip. Performs a standard Zip (lossless) compression to the image. Receiving application must have an unzip utility. ◆ JPEG. Performs lossy (image loss) compression to the image. ◆ IBM PC. Select PC if the image is to be used on an IBM system. Works also on Macintosh systems. ◆ Macintosh. Select Macintosh if the image is to be used on a Macintosh system. ◆ Save Image Pyramid. Check to save the image using several image resolutions. Lets you decide what resolution to use when reopening the image. ◆ Save Transparency. Check to preserve any transparent areas in the active image. ◆ RLE. Run Length Encoding (RLE) helps to compress solid areas of color across multiple layers. ◆ ZIP. Uses the Zip format to compress multiple layers. ◆ Discard Layers and Save a Copy. Creates a copy of the file without the layers, essentially saving a composite image file. Click OK. 8 7 7 8 Getting the Best Results on an Inkjet or Laser Printer Since your monitor displays an image using light and a desktop print- er reproduces an image using inks, dyes, or pigments, it is impossi- ble for a desktop printer to reproduce all the colors that can be dis- played on a monitor. However, by incorporating certain procedures (such as color management) into your workflow, you can achieve predictable results when printing your images to a desktop printer. For more information on getting the best color results, see Chapter 18, "Managing Color from Monitor to Print.” For Your Information From the Library of Wow! eBook ptg 406 Chapter 16 Remember that raster images are all about resolution. Images have a specific scanned resolution (spi, samples per inch). Your moni- tor also has a native resolution (ppi, pixels per inch), as does output devices such as inkjet printers (dpi, dots per inch), and high- end presses (lpi, lines per inch). While all these terms may seem a bit complicated, they're not; they simply explain how much information is contained within the image. Most computer monitors are set to a fixed resolution of 72 or 96 ppi. Say you scan a 4 by 4 inch image at 288 spi (that's 4 times the resolution of a 72-ppi monitor). If you attempted to display the image at 100% view, the monitor would take the image pixels and adjust the width and height to match its reso- lution, so the image would be 16 by 16 inches (288 divided by 72 = 4). If the display of the image doesn’t fit the size of your monitor and you attempt to reduce the magnification of the image to make it fit the monitor size, Photoshop will have to remove pixels from the image to make it fit. This typically causes the image to generate jagged lines, especially around angles. The moral of this story is: when adjusting an image for viewing on a monitor (for example, when preparing a slide presentation), never change the zoom of the image to fit the monitor; always adjust the resolution by selecting the Image menu, and then clicking Image Size. When it comes to output, such as to an inkjet printer, the rules are a bit more forgiv- ing. Many output devices have print resolu- tions of 1,440 or higher. However, we're not talking about fixed monitor pixels (ppi), we're talking about dots of ink hitting a piece of paper (dpi). Most inkjet printers, because of the dot gain of the inks (that's the amount of space over which a dot of ink spreads when it hits the paper), do not need image resolution greater than 300 spi. Although image quality suffers when you enlarge an image beyond its original size for viewing on a monitor, if you use higher resolutions than needed when you print, the image won't be degraded; you'll just be printing an image with a larger file size. However, that can be a waste of time. For example, a 300 spi, 8 by 10 inch image will have a file size of about 20 MB; the same image scanned at 1,200 spi will pro- duce a 329 MB file size. When you print the two images, you will probably not notice any difference in quality; however, it will take, on average, 6 minutes longer to print the 1,200 spi document on most mid-range printers. The bottom line is that resolution repre- sents the amount of information contained within a linear inch; however, various devices handle that same resolution differently. The good news is that understanding those differ- ences helps you to create a useable work- flow. Knowledge is power. Understanding Monitor, Image, and Device Resolution From the Library of Wow! eBook . publishing. The optional JPEG 2000 format plug-in can be found on the Photoshop CS5 installation CD in Goodies/Optional Plug- Ins /Photoshop Only/File Formats. Currently, only computers with the necessary. (Standard). The format is recognized by most browsers. ◆ Baseline Optimized. Produces optimized color, and a slightly smaller file size, but is not supported by older browsers. ◆ Progressive ptg 400 Chapter 16 Reducing the size of a photograph presents its own particular set of problems, and Photoshop comes to the rescue with solutions. For pho- tographic images, the best