Software :: Gigs Of Invisible Photo Files When Download From Camera?

Recently spotted a weird thing happening when I download images from my Nikon D200. I use Image Capture, but not sure if that's the problem. Maybe it's not a problem - hopefully you guys can help.Basically, when burning a DVD of images for a friend, I noticed that if I dragged over the folder that contained the downloaded images, the disc size in Toast matched the size of the folder, but that if I created a blank disc and just copied over the folder contents themselves, not the actual folder, the disc size was 1.5GB smaller.

So, I fired up TinkerTool and turned on Invisible Files in the Finder, and was shocked to discover that throughout my hard drive, in the folders I download photos into from my camera there are invisible 'photos' with a period at the start of their name (rendering them invisible) that are the size of a full high res photo each - essentially doubling the size of the folder. If I delete a photo in the Finder, it's invisible counterpart doesn't get deleted with it - so what the heck are they? They're taking up GB upon GB upon GB of space on my drive and I can't even see them unless I use TinkerTool.