TITLE
    Color LaserWriter 12/600 PS: 4-Pass and 1-Pass Printing
Article ID:
Created:
Modified: 		18190
7/17/95
2/3/99
TOPIC

    When I print a grayscale picture on the Color LaserWriter 12/600 PS, I notice that the printer still uses the four-pass printing mode. Why is this, and is there any way around this? Also, what does the printer look for when determining if it is going to use the single-pass or four-pass mode?

DISCUSSION

    Four-pass printing (which uses all the cartridges, CMYK) is not automatic when Color/Grayscale is selected in the Print dialog of the LaserWriter 8.3 driver. On the Color LaserWriter 12/600 PS, the printer controller primarily determines whether to switch between single-pass and four-pass printing modes. It does this by parsing the PostScript input stream for any "color information". If found, the printer is placed into four-pass mode by the controller. The following should help in characterizing the manner in which the Color LaserWriter 12/600 PS is placed into four-pass mode:

    The Color LaserWriter 12/600 PS WILL be placed into four-pass mode IF:

    - The document to be printed contains a bitmapped image, black and white or color (in other words, if the PostScript "image" operator is used).
    - It would take an enormous amount of "processing" time in the printer to look at the bitmapped data to check for any color information.
    - The document to be printed contains one or more non-black pixels.
    - If the entire page has only black and white data, but there is one color pixel in the page, then the printer will go to four-pass mode.
    - An EPS file being printed contains any references to color usage.
    - If the EPS file uses PostScript "color operators" such as "setcmyk", the printer will go into four-pass mode even if "Black and White" is selected in the driver.
    - The document to be printed is a Legal-sized page, and there is only 12 MB of RAM in the printer.
    - An application uses anything other than the PostScript "setgray" operator.

    Note: An exception to this occurs if only black and white text is being printed. In that case, the printer will use single-pass mode. Otherwise, the reasoning for going into four-pass mode is strictly for less memory usage.

Document Information
Product Area: Printers
Category: LaserWriters
Sub Category: Color LaserWriter 12/600 PS

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