Canon MultiPASS C50 Service Manual page 248

Part 2: Printer
2.7 Printing Modes
2.7.1 Printing mode
Depending on the cartridge installed, the medium, the printing mode, the resolution, the print data, etc.,
the printer varies the carriage movement, bubble jet head driving frequency, etc., to attain high-quality
printing without any bleeding or shifting in the printout.
When the 720 dpi printing/smoothing feature is used, the carriage feed pitch is set to 1/720 inch.
Although this slows down the carriage speed, the bubble jet head drive frequency (ink ejection frequency)
is increased so that the overall printing throughput decreases.
During color printing at a single pass, the different colors printed at the same time overlap, often causing
the colors to run. By printing with three passes, color bleeding is less prone to occur since the color
printed immediately before is stable by the time the next color is printed over it.
When print data is processed internally by the printer, the data is recognized and the number of ink
nozzles to be used by the black ink is changed automatically.
For color printing with Color-HQ2, at 720 dpi, processing is executed in such a way to prevent the color
and black inks from running at their mutual borders and to prevent white mist.
This processing is executed as follows:
During internal processing by the printer, the borders where the color and black inks meet are identified.
Cyan and black ink are mixed in the printed black portion to suit the state of the distance and density of
the black and color dots.
The printing method for the respective printing modes are listed below.
2.7.2 Photoprint mode
Photoprint mode can be used to obtain high level gradation print quality when using the Photo BJ
cartridge. These cartridges contain a light density ink which achieves a high level of gradation by
printing several times over the same dot.
The printer driver divides the pixel data into a maximum of 4-values (not printed, print 1 dot, print 2 dots
and print 3 dots) enabling each pixel to be printed in up to 4 gradations. The printer therefore makes three
passes using a maximum of 400% more ink than usual.
It is therefore necessary to use the exclusive print driver when printing with the Photo BJ cartridge.
The exclusive printer driver outputs multiple print data to the printer when photoprinting. If for some
reason, a standard color BJ cartridge is installed and used for photoprinting, everything printed will be
doubled in size in the carriage direction.
On the other hand, if color printing is performed with a Photo BJ cartridge, not only will printed images
appear light, the user will be notified of a mis-match as images will be printed in half their normal size.
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