How to Get Your Scanner Settings Right in the First Place

Your scanner software will have a set of simple choices for the kind of scanning you want to do. If these deliver the right results then stick with them, but if you want more hands on control you'll need to understand a little more about what is involved with making a good scan.

The most important thing to understand when choosing custom scanner settings is image resolution. This is all about "pixels per inch" (often called dots pen inch). Scans are made up of tiny squares of colors, the pixels, in a regular grid. The tinier the squares, the more detail the scan can hold but with tinier squares (more pixels per inch), the graphic will take more room on your disk and take longer to print and to email to someone. The trick is to scan something so that it has enough resolution for what you want, but no more. If you're scanning something just to show it on screen it doesn't need to be captured with nearly as much detail as when you want to use it in a print. 72 pixels per inch are perfect; if your scanner offers 75ppi that's close enough.

If you want to print scans that look as good as the originals, aim for at least 200ppi and preferably 300ppi or so. Anything lower and details will start to be lost. For scanning and printing documents with type or other kinds of sharp, fine lines, the image you scan should be at least 300ppi and preferably higher.

Where this can get a little more complicated is when you want to enlarge or reduce the original. If you scan a picture at 300ppi but then print it out at twice the size, you're simply enlarging the pixels along with the image. The result is an image printed at a 150 "effective" pixels per inch; you've stretched the 300 per inch to cover twice as much space. Don't worry too much about the math of all these, just get a feel for the basic logic so you won't end up with images that are too crude and blocky or so large that they take an age to print.

With originals that don't need to be captured in color, you should scan in grayscale mode or black and white to save memory. It takes only a third as much memory to work with a grayscale image as it does a full color one, and pure black and white graphics take 1/24th as much space as color. Do remember that black and white scans are less forgiving of low resolutions; they show pixilated edges in stark, high contrast relief. OCR scanning software normally captures pages in very high resolution black and white to make the letter shapes stand out as clearly as possible.

If you want to scan a form or official document so that you can print copies later, pick a high resolution and scan in grayscale or black and white if possible. Don't save this kind of image as a JPEG, because this format will cause visible damage and blurring to what should be crisp text and lines. Saving as a TIFF (compressed or not) or GIF (for grayscale and black and white scans) is a much better choice.

Finally, remember to use the cropping tool when scanning. Don't scan the full area if you just want a small section; preview first to see things properly, and then make your selection before continuing on to the Scan button. Your scanning software may have an option to do this automatically for you, but check that it has got it right before you go ahead and scan.

You may find that your scanner consistently makes the images it produces a little too dark or light. If so, you can often correct this before you make your scans. It is worth getting the settings right in the first place, because you'll get better, cleaner pictures as a result. The options you have depend on your scanner's software. Brightness and contrast sliders will be fairly obvious if you have them. Adjusting the white point and black point tells the scanner what it is to regard as the lightest and darkest pants of the image. Start with the standard settings, but if the image needs any overall adjustments, see if you can set these up to happen when you scan rather than afterward.