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Optimal Settings

The type of output device you use will determine the correct resolution setting for scanning or printing your image. Below you'll find the correct resolution settings for the most common types of output devices. You can use lower resolution settings than the ones listed below; but if you do, you will be sacrificing quality for the convenience of a smaller file size.


A Web browser can't change the size of the pixels that make up your screen (only your operating system can do that), so the browser completely ignores the file's resolution setting and just looks at its width and height in pixels. That means that a 100-by-100-pixel image will look the same in a Web browser whether its resolution setting is 300 or 72.

The following table indicates how much information can be displayed on most common monitors. If you create an image that contains more information than the monitor can display at one time, the edges of the image will be clipped off. To view the entire image, you will need to scroll. Or, if your image doesn't contain enough information to fill the monitor, there will be extra black space around the image.

Figure 4.12. For multimedia, think of the width and height in pixels instead of the resolution setting.

Table 4.1. Monitor Settings and Usage
Resolution % Used
640 by 480 7.5%
800 by 600 51.3%
1024 by 768 26.6%

Data on the percentage of Web users on each type of monitor was obtained from WebSnapshot.com

When I create graphics destined for the Internet, I always think about what type of monitor will be most commonly used to view my site. I work on a monitor that displays 1280 by 1024 pixels; most people use a monitor set to 800 by 600 pixels. To get a better sense of what my site will look like to the part of the world using smaller monitors, I change my monitor settings to 800 by 600 in the Monitors (Macintosh) or Display (Windows) control panel, open a Web browser, and take a screen shot. Then I open that screen shot in Photoshop and design my Web site within it. That way, I know exactly what it will look like on a smaller monitor, but I'm not forced to use the same settings. I also like to add guides to indicate where the edge of a 640-by-480 monitor would be, so that I can always keep in mind what my site will look like on the smallest monitor that might be used (Figure 4.13).

Figure 4.13. Try to keep critical information within the guides, which represent the smallest screen that will be used to view your site.

If you were to measure how large the pixels appear on most monitors, you'd find that between 72 and 96 pixels are visible in each inch. That means that in order to reproduce an image close to its original size, you have to use a scanning resolution between 72 and 96. If you want the image to be larger or smaller, then open the screen shot of the Web browser, make a selection to indicate how much space you'd like your image to take up, and look in Photo shop's Info palette to determine the width and height in pixels. Once you've found that out, you can divide the desired width (in pixels) by the physical width of the original (in inches), and the result will be the scanning resolution needed to end up with the desired size.

Or, if you don't like dealing with rulers and math, try this: Scan the image with a really high scanning resolution (such as 300). Then zoom out on your image by typing Command-minus (Macintosh) or Ctrl-minus (Windows) until the image becomes the size you'd like it to be in a Web browser. Note the percentage that appears in the bottom left of the document window. Now, choose Image > Image Size, check the Resample Image checkbox, change the Width pop-up menu to Percent, and then enter the number at which you were viewing your image. After you've completed those steps, your image should be the desired size when you view it at 100%.


When preparing images for the Web, you always need to be thinking about three things: the size of the smallest monitor that might be used to view your site (typically, a 640 x 480 monitor); the size of the most common monitor that will be used to view your site; and the browser interface, for which you'll have to leave room. The browser interface usually takes up at least 50 pixels out of the width and up to 115 pixels out of the height of your image. The exact height depends on which browser is being used and how many button bars are visible at the top of the browser window. For more information about preparing graphics for the Web, be sure to check out the fourth section of this book, starting with Chapter 15.

If you're scanning an image to be used for multimedia (such as CD-ROMs or games) and you'd like to scan an image so it will completely fill the screen, try the following technique: Divide the width of the monitor, measured in pixels (see Table 4.1), by the width of the original image, measured in inches. The result is the exact scanning resolution needed to capture enough information to fill that specific screen size.

Halftones (Laser Printers, Printing Presses)

Most popular printer types (such as laser printers, imagesetters, printing presses, and thermal wax printers) cannot truly reproduce shades of gray. They either leave the paper white or turn it pure black. To simulate shades of gray (or tints of color), they use something called a halftone. Halftones fool your eyes into thinking they see grays when they're really looking at pure black and pure white (or pure color). The halftone does this by substituting small black circles for the shades of gray, using larger circles for dark shades and smaller ones for the light shades (Figure 4.14).

Figure 4.14. Halftones use different-sized circles to simulate shades of gray or tints of color. (© 1998 PhotoSpin, www.photospin.com)

A setting called lines per inch, or simply lpi, determines the spacing of the circles used to simulate shades of gray. It's not called circles per inch, because you don't always use a grid of circles (you can use ovals, diamonds and other shapes). As the circles get packed closer together (higher lpi settings), the amount of detail your printer is capable of reproducing also increases (Figures 4.15-4.17). Higher lpi settings are usually more desirable because of the increased detail that results. However, as you pack more circles into each inch, the circles get smaller and are more difficult to reproduce on a printing press (the smallest circles start to disappear). Therefore, the printing process usually dictates the highest lpi setting that can be used. The following table shows the most common settings used and the defaults that are built into laser printers. The default settings are used whenever you print from a program that is not designed for publishing (such as spreadsheets or databases).

Figure 4.15. The image at 53 lpi.

Figure 4.16. The image at 85 lpi.

Figure 4.17. The image at 150 lpi.

Table 4.2. Common LPI Settings
LPI General Use
85 Newspaper advertisements
100 Newspaper editorial section
133 Magazines and brochures
150 High-end magazines and high-quality brochures
175 Annual reports and high-end brochures
53 300 dpi laser printers
106 600 dpi laser printers
212 1200 dpi laser printers

Whenever you scan an image that will be printed with a halftone, you'll need to know the lpi setting before you scan the image, because it dictates how much detail you're going to get out of your printer. Once you know the lpi setting, multiply it by 1.5 if you would like your image to appear as sharp as possible, or multiply it by 2 if you want it to look a little soft. Then use the result as your scanning resolution. Use the soft setting for portraits (unless you really don't like the person); otherwise, every pore on his or her face might show.

You can use Photoshop as a calculator by choosing Image > Image Size and then clicking the Auto button. Next, enter the lpi setting you are going to be using, and then choose Good if you want detail (lpi x 1.5) or Best if you want your image to appear soft (lpi x 2). Once you click OK, the resolution setting will show you the scanning setting necessary to achieve the result you desire.


The inkjet settings given here are what the inkjet printer manufacturers recommend. I find that you can usually get away with lower settings as long as your image does not contain high-contrast straight lines. So if you have an image of a sailboat (the mast is a high-contrast line), for example, then use the settings above; otherwise, experiment with lower settings.

The lpi setting we have been talking about is not directly related to your printer's dpi setting. You can have a 600 dpi printer and print with any number of lpi settings. But it is the lpi setting that determines how much detail you will get in the end. You can specify an lpi setting to print with in the Page Setup dialog box of most publishing-oriented programs. Programs that are not designed for high-end publishing (like spreadsheet and database programs) will use the default setting that's built into your desktop printer.

Inkjet Printers

Most inkjet printers do not use halftones to simulate shades of gray; instead they use what appear to be random dots. To simulate grays, they pack these same-sized dots close together for dark shades or space them farther apart for light shades (Figure 4.18). That's why if you look closely at the output from an inkjet printer, it might look noisy (like a TV set that doesn't have a station tuned in).

Figure 4.18. Inkjet printers use same-sized dots to simulate shades of gray or tints of color.

To find out the scanning setting needed for images that will be output on an inkjet printer, just divide the resolution of the printer by 3 (or multiply it by .33). Example: inkjet printer resolution = 720 dpi, 720 x .33 = 238 ppi scanning resolution.

Line Art

Images that contain only pure black and pure white—no grays—are known as line art (Figure 4.19). The most common types of line art are logos and text.

Figure 4.19. Line art images contain only pure black and pure white.


To find out more about line art scanning, see Chapter 5.

To get the highest-quality line art (regardless of what type of printer you are using), you'll need the pixels in your image to be the same size as the dots your printer uses. To accomplish that, find out the resolution of your printer (measured in dpi), and type that number into your scanning software where it asks for a resolution setting. The highest setting you should ever need is 1200. Settings above 1200 create overly large file sizes without noticeable improvement in quality.

Dye-Sub Printers

Unlike lasers and inkjets, dye-sub printers are capable of reproducing 256 shades of gray and/or 16.7 million colors. The output from a dye-sub printer looks just like a real photo (Figure 4.20). To get the highest quality from a dye-sub printer, you need the pixels in your image to be the same size as the dots the printer uses. To accomplish this, find out the resolution of the printer, and use that number for the resolution setting in your scanning software.

Figure 4.20. Dye-sub printers can truly reproduce the shades of gray and colors that appear in your images.

35 mm Slides

When you want to output an image to a 35 mm slide (Figure 4.21), you use a device called a film recorder. The type of film recorder used determines the amount of information needed in your image. The resolution of a film recorder is measured in K (usually 2K or 4K). The K stands for 1,024 and indicates how many pixels can be reproduced in the width of a slide. So a 2K film recorder can reproduce 2048 pixels (2 x 1024) in the width of a slide. The ratio between the width and height of a 35 mm slide is 3:2.

Figure 4.21. For slides, think of the width and height in pixels instead of the resolution setting. (© 1998 PhotoDisc)

Use the following technique to determine the scanning resolution needed to capture the exact amount of information that a 35 mm slide requires. First, determine how many pixels your film recorder can reproduce in the width of a slide (Table 4.3), and then divide this number by the width of your original image measured in inches. The result is the exact scanning resolution necessary to capture the proper amount of information.

Table 4.3. Film Recorder Specifications
Film Recorder Width and Height (in Pixels) File Size (in Photoshop)
2K 2048 by 1365 8 MB
4K 4096 by 2731 32 MB
6K 6144 by 4096 72 MB

If you find it too difficult to determine the width of your original (because it's so darned small), then try this approach. In your scanning software, crop your image and adjust the resolution and scale settings until your software indicates that the file size will be the same as what's listed on the right side of the table above. No matter what your scanning settings are, if your file size ends up being correct, then you should have the proper amount of information for that type of slide.

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