Adobe ADBCD17648MC Manuel D’Utilisation

USING PHOTOSHOP ELEMENTS 8
Understanding color

An image mode determines the number of colors that can be displayed in an image and can also affect the file size of 
the image. Photoshop

  Elements provides four image modes: RGB, bitmap, grayscale, and indexed color. 

Uses one of two color values (black or white) to represent the pixels in an image. Images in bitmap mode 

are called 1-bit images because they have a bit depth of 1. 

Uses up to 256 shades of gray. Grayscale images are 8-bit images. Every pixel in a grayscale image has 

a brightness value ranging from 0 (black) to 255 (white). Grayscale values can also be measured as percentages of black 
ink coverage (0% is equal to white, 100% to black). 

Uses up to 256 colors. Indexed-color images are 8-bit images. When converting into indexed 

color, Photoshop

  Elements builds a color lookup table (CLUT), which stores and indexes the colors in the image. If a 

color in the original image does not appear in the table, the program chooses the closest one or simulates the color 
using available colors. By limiting the panel of colors, indexed color can reduce file size while maintaining visual 
quality—for example, for a web page. Limited editing is available in this mode. For extensive editing, you should 
convert temporarily into RGB mode.

When you choose a different color mode for an image (Image  > Mode

  > [image mode]), you permanently change the 

color values in the image. You might want to convert into a different mode for several reasons. For example, you may 
have an old scanned photo in grayscale mode in which you want to add color, so you would need to convert it into 
RGB mode. Before converting images, it’s best to do the following:

•

Edit as much as possible in RGB mode.

•

Save a backup copy before converting. Be sure to save a copy of your image that includes all layers in order to edit 
the original version of the image after the conversion.

•

Flatten the file before converting it. The interaction of colors between layer blending modes will change when the 
mode changes.