Low res images

I started testing low resolution images on this machine. As I expected, the 72 dpi images looked pretty bad. I then opened a 300 dpi image. The original image was 4x5, so I decided to try printing it at twice it's normal size. I was amazed at how well it printed. There was no pixelation. I then proceeded to print it at for times it's normal size. With an initial resolution of 300 dpi, this would equal 75 dpi at it's new size. To my amazement, it still looked really good. I can only assume that the RIP is using some type of interpolation to smooth out the image. I then enlarged the image even father, to 8 times it's normal size, and I finally started to see some of the pixelation I was expecting.