I used all the 5D Mark 1 2 and 3 before I switched over to Sony mirrorless. You would notice a big improvement from a 6d to a 5D Mark III or higher. The big game changer when you go mirrorless is having the camera scan the scene look for eyes and focus right on them for you. USED Canon EOS 5D Mark III Digital SLR. Opens in a new window or tab. Pre-Owned · Canon EOS · Digital SLR. 5.0 out of 5 stars. 462 product ratings - USED Canon EOS Acmy.