Is the interpolation we're talking about the process by which the resolution of your image is adjusted to match the resolution the printer is set to print at?
Yes, that is spot on. Mike did an article related to this here:
http://ddisoftware.com/tech/articles/march-2010-smart-photo-printing/However, I'm not sure what sharpening means here. My understanding of sharpening is adding outlining to areas in a picture to help them stand out. I don't want to add any "artifacts" to the pictures I am printing. I need faithful reproductions of what I am printing. What does this sharpening do?
"adding outlines" is not quite correct, USM (un-sharp mask) is about modifying contrast across boundaries. see here:
http://www.cambridgeincolour.com/tutorials/unsharp-mask.htmIf you see artefacts, halos and outlines at normal viewing distances, then there is too much sharpening.
Most digital images are sharpened to some extent: Jpegs out of camera, even if the menu allows you to turn it down. Raw images will usually have some sharpening applied during conversion otherwise the image would be very soft and most conversion processes allow you to adjust that along with noise reduction. QU has excellent control for this and once set for a camera, will usually not need any more adjustment.
The final print sharpening is a form of USM but is "smart" in that it's adjusted according to the print being made; as the Help says factors such as size & resolution are taken into account, and normally be set (and left) so your print looks the same as the image on screen with respect to sharpness.
I would say sharpening of digital images is all part of "the illusion" to trick your eyes & brain into making an image look like real life
I need faithful reproductions of what I am printing
Smart print sharpening actually helps you to achieve this just as colour management help to get the print colour the same as on screen.
Terry