Pixels and print quality

When mulling over resolution options, your first consideration is how large you want to print your photos, because pixel count determines the size at which you can produce a high-quality print. If you don't have enough pixels, your prints may exhibit the defects you see in the pixelation example in Figure 3-1, or worse, you may be able to see the individual pixels, as in the right example in Figure 3-4.

Depending on your photo printer, you typically need anywhere from 200 to 300 pixels per linear inch, or ppi, of the print. To produce an 8-by-10-inch print at 200 ppi, for example, you need 1600 horizontal pixels and 2000 vertical pixels.

Table 3-2 lists the pixel counts needed to produce traditional print sizes at 200 ppi and 300 ppi. But again, the optimum ppi varies depending on the printer — some printers prefer even more than 300 ppi — so check your manual or ask the photo technician at the lab that makes your prints. (And note that ppi is not the same thing as dpi, which is a measurement of printer resolution. Dpi refers to how many dots of color the printer can lay down per inch; most printers use multiple dots to reproduce one pixel.)

Table 3-2 lists the pixel counts needed to produce traditional print sizes at 200 ppi and 300 ppi. But again, the optimum ppi varies depending on the printer — some printers prefer even more than 300 ppi — so check your manual or ask the photo technician at the lab that makes your prints. (And note that ppi is not the same thing as dpi, which is a measurement of printer resolution. Dpi refers to how many dots of color the printer can lay down per inch; most printers use multiple dots to reproduce one pixel.)

Table 3-2

Pixel Requirements for Traditional Print Sizes

Print Size

Pixels for 200 ppi

Pixels for 300 ppi

4 x 6 inches

800x1200

1200x1800

5 x 7 inches

1000x1400

1500x2100

8 x 10 inches

1600x2000

2400 x 3000

11 x 14 inches

2200 x 2800

3300 x 4200

Even though many photo-editing programs enable you to add pixels to an existing image, doing so isn't a good idea. For reasons I won't bore you with, adding pixels — known as resampling — doesn't enable you to successfully enlarge your photo. In fact, resampling typically makes matters worse. The printing discussion at the start of Chapter 9 includes some example images that illustrate this issue.

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Reasonable care has been taken to ensure that the information presented in this book is  accurate. However, the reader should understand that the information provided does not constitute legal, medical or professional advice of any kind.

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