when I'm adding images to a post and choose to have them link to a page, the wordpress links it to an attachment page where as surfers can leave comments directly related to that attachment. However the image file that is displayed on the attachment page is a medium sized one (the resize is automatically created by the script during upload).

How do I make it so attachment pages display full res image, instead of that medium res one?

The same goes for [gallery] option - it's a handy little feature, but again, it links to an attachment page that displays a medium sized image and that medium sized image is then linked to a .jpg file itself. I would rather have the original .jpg file displayed on the page and not have it linked. How do I achieve that?