I like the Mamiya Super 23 and Universal for older generation good users in the field. With some holders you can use 645, 6x6, 6x7 and 6x9 formats. Also, with the Universal you can use Polariod. And the system has lenses from 50mm up to 250mm. The Super 23 has a bellows in the back for closeup work, too. More modern, the RB67 is a great system that has a macro capability with a bellows in the camera body. The Rollei SL66 system has macro capability and some limited movements for the camera lens, but is somewhat more expensive. I like 4x5 even though it is somewhat more time consuming to use to use than a 6x7 which can get up to 20 shots on 220 film.