We make physical prints by either applying ink to paper or by exposing photographic paper to light.
You’re already familiar with the first process. Ink comes in different colors, plus black, a printer applies the ink to paper and, voila, you have a print.
If you took a photography class in high school or college, you probably used the second process. You took a photograph, exposing the film to light. In a darkroom, you developed the film using chemicals to get a negative. You put the negative into a projector and used the projected image to expose photographic paper. Then you developed the paper (again using chemicals) and that was your print.
This may surprise you, but print companies generally use the second process to print your digital photos. How do they do that? After all, you send them a digital file, not a physical negative.
High-end photographic printers do not use ink the way your desktop printer does. Instead, they use light. A laser exposes true photographic paper to light based on the information in the digital file.
Then the exposed photographic paper needs to be developed with chemicals. In modern high-end photo printers, this happens inside the printer itself. So while high-end photo printers don’t have “ink cartridges,” they do have “chemical cartridges”!
I did some research on the print processes my favorite three labs, Smugmug, Mpix and Myphotopipe, use. Tomorrow I’ll post what I found out!