Thanks kb244, that's my understanding of how things are also.
I'm looking at getting 4x6's, 5x7's and 8x10's printed with an 8.2MP camera. However, here is a quote from White House Custom Color (www.whcc.com
):
"We request files in a very specific format to streamline both your workflow and ours when moving large amounts of images around, but keeping the highest quality image for output. Please follow these file requirements, if your files are not prepared correctly there will be a delay in your order.
• 300 PPI (except for large prints, see Thrifty Large Print section for more information)"
and,
"We request that all files be cropped to exact print size, with small prints at 300 PPI, and large prints with no interpolation (see Thrifty Large Print section for more information on resizing without interpolation). This is for two reasons. First, if you do the crop to exact print size, there will be no surprises in cropping when your image comes back. Our equipment can handle all sorts of aspect ratios and will center crop to make an image fit. If you crop it yourself, you have complete control and can easily adjust the crops from 8x10 to 5x7 aspect ratio prints. Secondly, cropping to exact size at 300 PPI removes excess image data that isn’t needed for printing smaller print sizes. This saves both you at the studio and us at the lab time in file transfer."
So, it looks like the only reason to set the ppi would be to reduce the information sent to a lab so you don't take up a lot of bandwidth and disk space ... since WHCC only print at 300 ppi anyway. WHCC also want images saved as jpeg compression 10.
I guess I'm still missing something ... I thought that most mini-labs were optical labs using wet chemistry, so if you sent them a high res (8.2 MP) image, all of the resolution would be used, even for a 4x6. If this is true, then WHCC must be using dye sub or inkjet, which isn't what I'm looking for from a lab (I could do that and print from home).
Bob