the image looks like a gray image yet it consumes much less disk space. Newspapers generally use halftone images. Since halftone is a type of black and white image, the disk space required is 1/24 of that required to save a 24-bit true color image.
8-BIT GRAY
A single-channel image consists of at least 256 shades of gray. An 8- bit scanner produces a greyscale image with 1024 shades of gray between pure black and pure white. Choose this option if you are scanning black and white photographs.
With 8 bits of color information per pixel, the file size of an image is eight times larger than a black and white image and 1/3 the size of a 24-Bit Color image.
8-BIT COLOR
An 8-Bit Color image provides 256 color hues in the image. The file size of a 256 color image is 1/3 the size of a 24-Bit Color image. Slight banding will be visible in areas which contain graduated color.
24-BIT COLOR
A 24-Bit Color image consists of three 8-bit color channels. The red, green, and blue channels are mixed together to create a combination of one billion colors which give a more true-to-life quality to the image. Choose 24-Bit Color if you are scanning color photos.