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HP_DeskJet_CMY printer driver

This driver was written for use with PCL 3 compatible printers which can print using *three* inks at the same time. This includes printers like the HP 500C or the HP 420C. It will also work on printers like the HP 880C or the HP 550C, but this is not recommended (the HP_DeskJet_CMYK driver will work better on these machines). Specifically, this driver was designed for printers which follow the CMY colour model.

The HP_DeskJet_CMY can also do greyscale dumps, but requires that you change the printing cartridge (remove the colour cartridge and replace it with the black cartrige).

Shingling and depletion

Shingling is a technique which works by interlacing individual printing passes, thereby increasing the amount of ink that hits the paper. Colour will be packed much denser with this technique, but printing time will increase since the printer`s head will have to make up to four passes on the same few lines to be printed.

Depletion is an intelligent ink reduction technique. If a lot of ink hits the paper, the paper may be unable to absorb it. In severe cases ink may even leak into other areas of the paper.

With the HP_DeskJet_CMY driver shingling and depletion are controlled by the print density settings:

1-3: No depletion, no shingling

4: 25% depletion, no shingling

5: 25% depletion, 50% shingling

6: 25% depletion, 25% shingling

7: No depletion, 25% shingling

Printing quality will increase as you increase the density. So will the time it takes to print. The printing resolution will increase, too: with densities 4-7 300 DPI will be used for printing.

Gamma correction

Without applying gamma correction, printouts will come out too dark.The HP_DeskJet_CMY driver can apply gamma correction, depending on the threshold settings. Threshold setting 1 will apply no gamma correction. Threshold settings 2-15 will make the printout progressively brighter. As experience shows, quality is best around threshold value 10.

Colour correction

The older HP CMY inkjet printers were unable to print a convincing grey due to how their CMY inks fused together. You didn`t get a grey out of mixing cyan, magenta and yellow but some sort of greyish dark green. HP would suggest that in order to print a good grey one should reduce the cyan component by about a third. This is what the HP_DeskJet_CMY driver attempts to do. Apparently, this doesn`t work so well with modern pigmented inks, i.e. the modern inks succeed in making a mix of cyan, magenta and yellow look grey.

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