Thierry de Coulon wrote:

> So. Then it's Linux, not the printers.
> 

Can you check how the printer is setup and where the conversion is done into
what format. It might be a matter of selecting the correct driver for the
printer. I don't have any HP 42xx, so I don't know exactly what should be
right configuration, but usually what you describe is a result of
convertion from something to something with loss of quality.

It looks like your Mac is using local driver to convert to format that is
accepted by the printer without loss of quality, while printing from linux
uses some odd driver to convert to something with the loss of quality. This
could be simply the DPI setting or the driver.

regards