Best folder structure for storing image in filesystem?

I am in the process of creating a website for a small company, with a catalog page which shows categories and listing of all the products. I have images for each product, stored in one folder per product, each folder containing the small, medium and large version of the file (for use in diff. places).

Is it recommended/more efficient to combine all small, all medium and all large images in one folder each, so that when a catalog listing is dynamically created using PHP / MySQL the server (shared hosting) doesn't have to look in 10 different folders, where there is one image each?

Would I notice with about 10 items开发者_运维技巧 per page/request? (total of about 500 products?)

How are the images created and prepared? I mean most image software stores one size per folder. If this would be kept there's no intermediate step necessary to move/copy the images. I guess efficiency is not much different.

May i ask if you use a framework for the site?