Pretty much whatever way you compress a photo, you'll reduce the quality. The usual ways are to reduce it's size (dimensions) in terms of pixels from say 3000 x 2000 for a 6MP sensor to 600 x 400 for web use. That's an immediate drop in pixels from 6,000,000 to 120,000. Once you've done that, either save for web or save as (the select a level of compression that leaves enough quality but reduces the file size to an acceptable level) in photoshop (including elements). BTW, if you're looking for sotware, photoshop elements is a lot cheaper than lightroom at around £55 for the latest version (8).