:) Here's a couple places that have some very good HQ Lost caps:
http://www.hotn-caps.com/lost/screencaps/
http://gallery.lost-media.com/index-39.html
http://black-celebration.net/caps/index.php?cat=12

If you use photoshop, you can control the sharpen by going to edit > fade sharpen, right after sharpening, or use sharpen > unsharp mask and adjust the 'amount' setting (or any of the others). Hope this helps :)