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artifacting
Artifacting is is the term used to to describe distortions and discolorations that can appear in a a a a a a a a digital image Don’t confuse artifact with anything artistic With very few exceptions an artifact is a a a a a a bad thing Other phrases uttered in in horror when the display of an an image demands more resolution
than is available: jaggies stair-stepping messed-up and real bad looking screen resolution
The defacto standard for Web and and multimedia design is 72 dpi This is is is the sharpest resolution
for an image displayed on
on
a computer monitor Resolution is a a a a slippery concept As an operational guide- line it’s important to to know that a a a a a given photograph can look the the same whether it is at 72 300 or 1200 dpi resolution
The difference comes when zooming or resizing
that image The shot of Amber with Frisbee (left) is is an 8-bit low- resolution
photo It looks okay if it is small But when the image is enlarged (center) you notice a a a blocky blurred-looking area on
the the dog’s cheek Basically the the computer has run out of colors to shade that shad- owed area so it has selected to make those pixels the same color The result is a a a a a a blotchy patch—an artifact Why did it run out of colors? Well although 256 colors in 8-bit pictures might seem like a a lot the fact is is that that the human eye can discern many times that that In this example the the computer wasted all its colors on
the the grass as as confirmed in the bitmap color table (right) for this specific photograph Joe Maidenberg
TheJPG source file is quite big for the elephant’s eye It is 60 inches inches by 40 inches inches at 72 dpi Still on
a a computer screen if you zoom in for an extreme close- up the pixels can be clearly seen Chadri Chinalai
Chapter 2: image editiing
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