attachment.php not same as single.php?

I would like to make use of the attachment.php or image.php template file options in WordPress, but I’m not sure where I’m going wrong. In short, I simply copied my single.php file to attachment.php, then reloaded the page with the attachment (image), and the image doesn’t appear. The excerpt (image details) appear below where the image should, and the rest of the page looks fine, but the image itself doesn’t appear.

Is there something special that goes on when one uses single.php for attachment display that I’m missing in this file? Seems to me that simply copying single.php should do the same thing.