I am printing stereograms (like in those Magic Eye books you've likely seen). I can generate them at DPIs ranging from 30 DPI to 300 DPI. My HP LaserJet Color M475 printer insists on printing them at 600 DPI, or worse, interpolate the raster image using ImageREt to look like 3,600 DPI. Any fiddling around of the image by the printer or any mismatch in the generated DPI and the printed DPI destroys the stereogram effect.
Is there a way to force the printer to print at lower DPIs, like 150 or 300?
I installed the UPD PCL 5 and UPD PCL 6 drivers, which HP claims will allow me to choose a lower DPI, but (of course) this does not work.
Here's one generated at 75 DPI (you may need to open the image in its own window to see the stereographic effect). You'll note that printing this with a printer set for 600 DPI destroys the effect).
It's based on this rendering:
Rafael didn't answer my question (how to change resolution on HP LaserJet Color M475 printer), but he did solve my problem (see accepted answer below). The pattern I was using to generate the sterograms contained a lot of detail. Any tweaking by the printer in an attempt to enhance the image (e.g. HP's ImageREt technology) interfered with an observer's ability to see the 3D image. Rafael's 2nd suggestion was to use a pattern that (and I'm paraphrasing a bit here) "contained more discrete elements, while at the same resolution as the problematic pattern." When I did this, the 3D image is readily apparent in the printed form, even with HP's ImageREt technology fiddling with the bits.
Here it is again, with the new pattern: