Originally Posted by Artoliver Wont the quality be better if the dpi / resolution is higher?

I was going to say, photoshop has variable DPI, like if you open a digicam picture its huge, and/or really high DPI. Maybe try setting it to 300DPI, or making the image size, 5x or so and then work with it shrunk down. Then printing it may take some extra effort, DPI can be changed in image size, or canvas size, i forget which.