There's a problem with bringing high-quality files to your local consumer photo joint or pharmacy photo hut. And that is that they're not expecting high-quality files. It's not that their machines can't print well (though often they're terribly calibrated, etc) rather it's that the computers in the printers are automatically pre-processing the files to make crappy pictures from your vacation look better.
I'm putting together a book of my Drabbles series I finished yesterday. My designer friend Kaytee is coming over tonight and we're going to piece the thing together as a maquette. Sit down on the floor and try them in different orders and that kind of thing.
So to this end I wanted to print all 46 images out as 4x6 prints to throw around. I burned a cd of medium res files, brought them down to my local mom&pop photo place and came back an hour later. 46 prints, $10, done. Some of the images looked great. Others looked terrible. They're fine for what I need tonight, but I was staring at them trying to figure out why some were perfect and others were so wrong. And I realized that it was the darker images which came out poorly. Because the computer on the printer doesn't expect a dark image, so it runs an auto-levels adjustment which pulls the lightest color to white and voila! your image looks like ass. So be careful.
Here are two examples. Original file on top, scan of print on the bottom. The photo of Lesley on the left came out great, that's because the lightbulbs around the mirror were already at white, so no processing was nessessary. By contrast the image of Henry on the right is very dark on purpose, as he is drinking is a dark bar. However the computer doesn't know about the dark bar, so it did what you see below.
I've thought about ways to counter this by putting black and white chips along the edges like the CMYK color marks, but that just seems silly, as I rarely get stuff printed there. Also interesting is that it works the same in film processing, where the negative is great, but the prints come back with highlights clipped because the computer goes a little too far in trying to maximize contrast. I know I could also tell them not to process them (if that's possible on their machine), but the proprietor is a very nice older Chinese couple and complex technical communication is not our best interaction.