Check the pixel count before you print

Resolution — the number of pixels in your digital image — plays a huge role in how large you can print your photos and still maintain good picture quality. You can get the complete story on resolution in Chapter 2, but here's a quick recap as it relates to printing:

✓ Choose the right resolution before you shoot: Set resolution via the Image Quality option, accessible via the Live Control and Super Control Panels as well as Shooting Menu 1.

You must set the resolution before you capture an image, which means that you need some idea of the ultimate print size before you shoot. When you do the resolution math, take any cropping you plan to do into account.

✓ Aim for a minimum of 200 pixels per inch (ppi): Depending on your printer, you may get acceptable results even at a lower resolution. On the other hand, some printers do their best work when fed 300 ppi, and a few request 360 ppi as the optimum resolution. However, using a resolution higher than that typically doesn't produce any better prints.

Unfortunately, because most printer manuals don't bother to tell you what image resolution produces the best results, finding the right pixel level is a matter of experimentation. (Don't confuse ppi with the manual's statements related to the printer's dpi. Dots per inch (dpi) refers to the number of dots of color the printer can lay down per inch; many printers use multiple dots to reproduce one image pixel.)

If you're printing photos at a retail kiosk or at an online site, the software you use to order prints should determine the resolution of your files and then suggest appropriate print sizes. If you're printing on a home printer, though, you need to be the resolution cop.

What do you do if you find that you don't have enough pixels for the print size you have in mind? You just have to decide what's more important — print size or print quality.

If your desired print size exceeds the photo's pixel supply, you have the following two choices, neither of which provides a good outcome:


✓ Keep the existing pixel count and accept lower photo quality. In this case, the pixels simply get bigger to fill the requested print size. When pixels grow too large, they produce a defect known as pixelation: The picture starts to appear jagged, or stairstepped, along curved or oblique lines. Or, at worst, your eye can make out the individual pixels and your photo begins to look more like a mosaic than, well, like a photograph.

✓ Add more pixels and accept lower photo quality. In some photo programs, you can use a process called resampling to change the pixel count. Adding pixels is known as upsampling; removing pixels is downsampling. Some other photo programs even resample the photo automatically for you, depending on the print settings you choose.

Although adding pixels might sound like a good option, it actually doesn't help. You're asking the software to make up photo information out of thin air, and the resulting image usually looks worse than the original. You don't see pixelation, but details turn muddy, giving the image a blurry, poorly rendered appearance.

To hammer home the point, Figures 5-15 through 5-17 show you the same image as it appears at 300 ppi (the resolution required by the publisher of this book), at 50 ppi, and then upsampled from 50 ppi to 300 ppi. As you can see, there's just no way around the rule: If you want the best-quality prints, you need the right pixel count from the get-go.

300 ppi

300 ppi

Figure 5-15: A high-quality print depends on a highresolution original.

50 ppi

Figure 5-16: At only 50 ppi, there aren't enough pixels to render details smoothly.

50 ppi upsampled to 300 ppi

Figure 5-16: At only 50 ppi, there aren't enough pixels to render details smoothly.

50 ppi upsampled to 300 ppi

Figure 5-17: Adding pixels in a photo editor doesn't rescue a low-resolution original.

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