Light copies I have changed all the cartidges and still have light copies

Hi katie44l:
Depending on the eviroment the printer is in depends on weather you have dust on the laser lenses. If you are in a dusty eviroment then the laser mirrors may have excessive dust on them preventing the laser beam from giving you the print quality that you need. The only way to fix this problem is to open the laser scanner motor assembly and clean the mirrors. That will require an HP certified technician to service the printer.

Image formation system
Laser printing requires the interaction of several different
technologies including electronics, optics, and electrophotographics
to provide a printed page. Each process functions independently and
must be coordinated with the other printer processes. Image
formation consists of seven processes:
Print cartridge
As the focal point of the image formation system, the print cartridge
contains toner and houses the cleaning, conditioning, and developing
stages of the process. The print cartridge contains the photosensitive
drum, primary charging roller, developing station, toner cavity, and
cleaning station. By including these components (which wear,
degrade, or are consumed) in the replaceable print cartridge, the
need for many service calls is eliminated. The special photosensitive
properties of the drum form an image on the drum surface and then
transfer the image to media.
CAUTION The print cartridge does not include a light-blocking shutter. Do not
expose the drum to light, which can permanently damage the drum.
Protect the print cartridge whenever you remove it.

Hope this helps.