photoshop and dpi

From: Angie


I sent a project to a printer, I upped a file with shapes and raster in it up to 1200 and then saved it as a Tif becaues I thought that's what the Print House printed their stuff at. We got a proof back where it looked like crap. all of the clean curved lines were all choppy and you couldn't read some of the smaller type. According to the printer, whatever you see on your computer, no matter what % you're looking at the image at. that is how it will turn out. Which doesn't make sense. at 5% yes it did look bad but at 12% it was fine. I've worked on projects before where if the percentage isn't an even 25% or something like that it'll look bad. Does this make sense to anybody? to anybody who could explain this better so I get it? thanks