Online Ordering, Sizing/Cropping Options

I've done a search here and can't really find any threads that have addressed this. I'm looking into online print sales. Lets say you have a photo, and customers have the option of printing a 5X7 or an 8X10 of that same photo. We will use these 2 sizes now to keep it simple.

How do you address the cropping issue with the print company? Do you simply process both sizes, upload them separately, label them accordingly by size, then restrict the purchase of sizes to the proper ratio (Customer see's duplicate images)?

Or is there some type of background file system that selects the properly cropped file, based on the size the customer orders, so the customer only see's one image to select?

11:15 is the exact median shape between the longest standard print shape (2:3) and the shortest (4:5).

When I'm providing files for customers, I crop them to 11:15 shape. That way, I'm ensuring the fewest nasty surprises possible.

It's all in how much control you want, how much you want to give to the customer, and how much to trust the printer!

I myself prefer to crop to a given aspect ratio for the best composition when printing large, and I use print sizes that "fit" that aspect ratio.

But for smaller print sizes, 4x6, 5x7 and 8x10, when other people are doing the choosing and ordering the prints and you don't have a defined print size they are ordering, you may be best off using a lab that gives them crop/layout options that they can choose and apply themselves onto an original-aspect ratio image. A 4x6 is the original ar, a 5x7 is cropped "a bit" off the wide ends, and an 8x10 is cropped a good deal more off the wide ends, and other print sizes will range between, like say an 11x14.