SCANNING AND COLOR CORRECTING TIPS

Continuous-tone (grayscale or color) images should be scanned to provide a final printed output at between 225 and 275 dpi. Final image dpi is the resolution in dpi of the original scan, divided by the enlargement or reduction factor. A 300 dpi scan reduced 50% provides a 300/0.5 or 600 dpi final image and creates a larger file than necessary. A better choice for a 50% reduction would be a 125 dpi scan, which would print at 125/0.5 or 250 dpi. A 600 dpi scan enlarged 250% provides a 600/2.5 or 240 dpi final image, and falls comfortably within our recommended range.

The example scans on this page show a photo scanned at 75, 150, 225 and 300 dpi and output at 100%.

The photograph above was scanned at 75 dpi and is not of acceptable quality for most applications.

Line Art Scan Resolutions

Line art (b&w) images should be between 600 and 1000 dpi. Images with a resolution lower than 600 dpi may exhibit jaggedness when printed.

Scan Formats

All scans should be converted into the CMYK format (not left in RGB) prior to importing the images into your page layout program. After the conversion, check the color content of the scan in CMYK as sometimes the color shifts are dramatic.

Rotating Scans

Scans (bitmaps) should be pre-rotated in Photoshop and not in your page layout program. Scans rotated in a page layout program print very slowly and require a great deal of extra memory.

Resizing Scans

Scans (bitmaps) should be pre-sized prior to placing them in your page layout program. Resizing scans in the page layout program forces the program to calculate the resize every time the file is printed.

Cropping Images

Crop scanned images as closely as possible prior to placing them in your page layout program. Cropping reduces the file size and speeds manipulation and printing of the image. Don't crop scans in your page layout programs. The portion cropped is still part of your document and creates a unnecessarily large document.

Color Correcting Your Scan

Though today's scanners and digital cameras do a very good job with color, even the best scans benefit from color correction. As you color correct your scans, remember not to trust the colors on your monitor. The monitor creates its colors with Red, Green & Blue light. However, your final printed piece will be in CMYK and the translation from RGB to CMYK is not always very accurate.

The only safe way to check the colors in your scan is to sample various parts of the scan with your program's eyedropper tool and compare the CMYK values returned with a color matching book. Though this procedure can be time consuming and is still not exact, it will greatly increase the likelihood that the colors of your printed piece match your expectations.

The photograph above was scanned at 150 dpi. Though better
than the 75 dpi image, this quality is still not acceptable in most instances
.

The above photograph was scanned at 225 dpi and provides good quality and reasonable file size.

The above was scanned at 300 dpi. The file size of the above scan is 77% larger than the 225 dpi scan, and provides very little noticeable difference.

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