MAMIYA 645 PRO & 645E
It wasn't long after I started shooting film that the inevitable happened: I was seduced by medium format (beyond my work with the Holga). Even the 6x4.5 format, the smallest of the medium format aspect rations, offers twice the image size of 35mm film and seem to create a wholly different look. Furthermore, medium format cameras themselves are designed completely differently than their 35mm relatives, adding a bit of intrigue.
The most common medium format cameras are modular SLRs, which consist of a body, film back, finder, and lens as well as other optional accessories. The Mamiya 645, Pentax 645, and Bronica ETR are common examples, each of which bringing something unique to the table. For example, the Bronica employs leaf shutter lenses (exclusively), which is great for flash shooters since you can sync at all shutter speeds. The Mamiya appealed to me because it can pair with the lens with the widest aperture for a medium format camera: an 80mm f/1.9. The Pentax is actually less modular; the film back , prism finder, and trigger grip are built-in. That said, the Pentax also allows simple adaptation of the fantastic lenses from the larger Pentax 6x7 SLR.
Modular system cameras are very useful for some people. Interchangeable film backs allow you to swap film types mid-roll, or shoot preview images on instant film. You can choose from waist-level finders, which allow you to look down onto a ground glass, or from traditional eye-level prism finders, both metered an un-metered. WLFs are lighter and provide a 100% view of the focusing screen, but can only be used for landscape-orientation shooting. Prisms are heavier and reduce the visible image area in your finder, meaning that you might get unexpected elements in your composition. Automated exposure is commonly only possible with metered prisms, but they're heaver and have a higher battery drain. System cameras also allow you to choose between hand-cranked film advance or a battery operated winding grips (which again add weight and bulk).
After a few rolls with the Mamiya 645 Pro, it was clear to me that image quality was significantly better than what I was achieving with my Holga, and certainly an improvement over the Lubitel. While I was happy with the images I was getting from the Mamiya, the ergonomics of this type of system were a challenge. The grip and metered prism, while great in the hands and useful for quick shooting, made the camera quite heavy. It was also very difficult to find a camera bag that could the camera comfortably; disassembly made things more compact, but also meant wasted time for set-up and break-down. It's also important to note that with the Mamiya, it wasn't possible to use a neck strap with the winding grip installed, as the grip covered the strap lug on one side.
At the time, I felt like I was holding an incredible piece of machinery, so I didn't those flaws. In hindsight, I prefer a tool that’s little lighter if lacking in features. I eventually sold the 645 Pro, but chanced upon a 645E later on. The 645E is a budget model with less options. It has a metered prism integrated into the camera, which includes a focus diopter (great for glasses-wearers). The 645E also sacrifices interchangeable film backs in favor of film inserts, which are smaller and just as fast to use in my opinion.
Modular SLRs can be a lot of camera and maybe not the best choice for a first camera. I'd argue that you could have just as much fun with the older M645 (often just referred to as the Mamiya 645), which is far more simplified but uses the same great lenses. It might be worth thinking about what features are necessary for the way that you shoot and the types of images you want to make. You could get into medium format SLRs for less than $200, or you could spend up to $4000 for a Contax 645 (which feature incredible Zeiss lenses - and autofocus). Remember, the camera is just a tool and a skilled artist can do a lot with a little.
Would I get another 645 SLR? I'm not so sure. For almost the same amount of money you can get a camera that shoots the larger 6x6, 6x7, 6x8, or 6x9 formats. While they burn through film a bit faster, they tend to be more fun to use and have a more unique look (especially 6x6 and 6x7). I'd certainly like to get my hands on Bronica RF645 rangefinder some day, and the Fujifilm GA645 series of autofocus point and shoot cameras are a real treasure. That said, 645 SLRs are a cost-effective way to shoot 120 film and get high quality results. I'm certain any photographer who loves film will find great joy in seeing the results of their first roll of film, and perhaps it'll ignite something in you like it did for me.