Datasheet

Why are there 256 levels?

This 256 number comes up a lot when talking about image modes. What

makes it so special?

Reproducing tone on paper or a monitor requires a minimum of about 200

tone levels to give smooth results without

banding (or making sharp transi-

tions between) the tones in smooth gradient image areas. Some images can

get along with far fewer levels of tone, such as highly textured images or

those that don’t really contain any smooth tones.

Two hundred tone levels is a kind of minimum benchmark for good results.

So why 256 levels and not exactly 200? It has to do with the way computers

calculate. Computers use binary math, and 8-bit encoding allows exactly 256

tone levels. Seven-bit would result in just 128 tone levels. So, 8-bit mode

became the minimum standard for full tonal range image files.

The 256 tone levels of 8-bit mode also allow a little headroom for file editing.

Image editing always causes some amount of information loss, and as a direct

result, an edited 8-bit file always has less than 256 real tone levels remaining.

The extra 56 levels allow more editing before any tone banding problems

become visible.

Understanding Color Modes

A color mode is a fancy term for the method Elements uses to display and

print your image. Elements allows you a choice of four different color modes.

And although Elements doesn’t support the CMYK mode, it can convert a

CMYK-mode file to a mode it does support.

RGB

You’ll probably use RGB, Elements’ standard default mode, 99 percent of the

time. This mode uses three channels (Red, Green, and Blue) to describe color

and tone. This mode is the most versatile and gives you access to all the edit-

ing tools and filters in your Elements application. RGB files allow embedded

color profiles (which we talk about in Chapter 4).

Index color

This is an ancient color mode in the computer world. Unlike RGB 24-bit

mode, with 16.7 million possible colors, index color allows only 256 colors.

This mode was originally created back in the old days as a means to keep

Chapter 1: Understanding Color

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