Bands in pictures printed from Preview (due to image expansion?)

When I print a color picure from Preview, areas of medium color like an evening sky show bands about one inch wide. parallel to the print head movement direction. So one inch tall band will be lighter, the next darker. These are subtle differences, but ruin the print. I've contacted Epson who told me to try all the things I had already tried e.g. clean, calibrate, & align printer, new Epson brad ink, etc. They said if that didn't work it was the computer, or the cable, which I find unlikely. So I then tried printing from Gimp and Picasa, which did not have the problem, but also printed at the correcct size instead of expanding the image to fit the paper. This happens with both small images 320X231 as well as large ones 1600X1200

I read a comment in the community written in 2009 that said "After you choose File -> Print, under the "Orientation" section, about halfway down, is a drop-down menu. Choose "Preview" in there. After that, use the Scaling options to get it to print the size you want." I tried that but it doesn't change the size of the printed image. I also tried fiddling with the image size on the Tools menu but that didn't help. It seems like the only way to shrink the image on the paper is to change to a smaller paper size, which is a workaround. So if anyone can point me to a way to scale down the printed image sizee I'd appreciate it.

Are these bands being caused by the expansion of the image? It's being blown up about 60%. Any thoughts?

Background: Preview version 5.0.3, OS 10.6.8, printer connected directly via USB. Printer is Epson Workforce 633