Huh? Doing a block copy from a disc (i.e. dd) will give you the 'cooked' image, in other words, the ISO filesystem image. Try it on a CD sometime. You will get a 2048 byte/sector ISO filesystem image.

Sometimes people refer to 'raw' images as ISO images and even tag them with an ISO extension, which is wrong. To get a raw image, you need a program to use the special device ioctls to read subchannel/ECC data, for example cdrdao does this. The resulting image is a 2352 bytes/sector image and cannot be loop mounted as an ISO filesystem.