What Is Dot Gain in Photography?

Dot gain can make photos look darker, muddier and not exactly the way you intend them to look when printed. It is not a function of the original photo---digital or film---or of the image-processing software you use, or even the screen on which you work. It is the result of the combination of the printer and the paper used.

The Phenomenon

Dot gain, essentially, is a phenomenon caused when ink from a printer hits the surface of the paper and sinks in. What happens is that the ink seeps into the paper and expands slightly. This causes the tiny dots that make up the finished photo print to get bigger and darker.

Types

This bleeding of ink is especially noticeable in screened images, those associated mostly with high-volume printing, such as in newspapers or magazines. In order to reproduce photos in a press run, each photo must be reduced to a series of dots of varying sizes for each color printed, cyan, magenta, yellow and black. This is called screening or half-toning. If you look at an image in a newspaper with a magnifying glass, you will see the dots.

Quality Counts

Dot gain varies depending upon the type paper used for printing. For example, newsprint, the paper newspapers are printed upon, is low-grade paper that "bleeds" ink across its surface. This is why newspaper images, especially black and white photos, can appear very dark even if that is not how they were toned in the newsroom. Better paper, especially coated or glossy paper, such as in magazines, does not allow the ink to spread much.

Solution

One fix for the dot gain problem is to tone photos lighter than you normally would. If you are printing to card stock or regular non-photo paper, bring the mid-tones up a notch or two and lighten the lights a bit. The photo may look a little washed out on the screen, but when printed to un-coated paper, it will darken. This takes a little experimentation to get the right balance.

Benefits

Some photos could benefit from dot gain. A washed-out photo that can't be toned darker without losing detail, for example, will gain both a darker tone and some depth wherever there are textures. While it is best to tone photos before printing, dot gain can help to fill them out a little.