Re: 256 levels of gray
Re: 256 levels of gray
- Subject: Re: 256 levels of gray
- From: Graeme Gill <email@hidden>
- Date: Thu, 17 Jul 2003 12:24:05 +1000
Rahul Kaushik wrote:
>
Do laser printers have 256 levels of gray with their halftone cells, or
>
256 levels of gray as part of the pure engine marking capabilities
>
(before halftoning)? Or someting else?
This depends on the engine in question. Many cheap, popular
laser engines are bitonal devices, so they simulate grey
levels with some form of screening. These types of engines
are often pushing for higher and higher bitonal DPI
(600 being a typical minimum, 1200 or even claims of 2400 DPI
being more typical), to counteract the poor resolution
resulting from screening.
The laser engines traditionally used in color copiers on
the other hand, have a lower DPI, but are true continuous
tone devices, being able to modulate both the laser amplitude,
and laser exposure for each pixel, resulting in a raw
control range of 256 values per pixel. Such true contone
laser engines generally run at 400DPI. Using proper anti-aliased
rendering, the result is generally a great deal better than
a 600 or 1200 DPI bitonal engine.
There are many devices around now that straddle these two
extremes, having an engine that might have effectively 2 or
4 bits per pixel control over the imaging engine, while
using screening to render 256 effective levels.
Graeme Gill.
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