Forum:KB:Turrets on star cruisers?

In all of the star wars movies (save episode 2), battleships such as star destroyers, CIS ships, Mon Calamari Cruisers and the like are shown firing lasers. However, (especially in episodes 4, 5, and 6) there is very little visual evidence of obvious turrets on star cruisers and battleships, other than the shots that they fire.

Can anybody post some pictures (preferably episodes 4, 5, and 6) that disproves this?