It seems (I think I figured it out) that when you caption a photo, the font looks fine as long as the original size is used. If you upload an image and say set it to LARGE, MEDIUM, or Thumbnail--or even adjust it via the percentages, it throws the fonts off and makes them large and bold.
Example http://www.eyeonannapolis.net/2009/0...senior-effort/
This original pic was 3648 wide when uploaded to WP. I used the preset to large and if you will notice the fonts get really bug bold and run into one another.