Its been a few months now since I started using the Mamiya as my main camera, and.. I have some thoughts. Let me first say that I consider the Mamiya RB67 to be the mother of all roll film cameras, and it's understandable that one who enjoys shooting film might gravitate towards this camera, as I did. They're fully mechanical, the negatives are huge, the lenses are sharp as fuck, and the process of working with it is really enjoyable, at least in my opinion. It's an overall phenomenal camera, and I would be more surprised if a hardcore film shooter didn't want one, to be honest. Maybe thats why they continue to disappear from the used market. Before you jump into getting one like I did though, there are some things you definitely need to know about it first.
First and foremost is that, although its a very appealing camera, it isn't going to be for everyone. The RB67 is an incredibly slow camera to use, and therefore it is definitely not for all applications. As a general rule, If you wouldn't shoot something on a tripod, this camera is not for that application. Even if you don't plan to use a tripod, this camera is so cumbersome that it won't make much of a difference workflow-wise whether you do or not. It's great for things like landscapes, portraits, and other still subjects, but in my opinion genres like sports and candid street photography are off the table for this beast. I find it almost akin to a scaled down view camera in the way it operates, and it is often extremely slow. Like a view camera, film for Mamiyas can be really expensive too. Trust me when I say you will really burn through film on cameras like these, so I wouldn't recommend them for use in a "documentarian" capacity, because you have to be somewhat selective with what you choose to shoot.
Low light and night photography pose another challenge with this camera, for two reasons. The first is that the shutter speeds, which are located in the lenses, top out at 1 second, and only have time exposures, no bulb. While this is okay for longer shutter speeds, It makes anything between 1 and ~ 4 seconds somewhat inaccurate, because you have to physically move around parts on the camera to stop the exposure while trying not to introduce any motion blur by shaking it. The other problem is that it is extremely difficult to focus in the dark. The vast majority of these cameras have no split prism in their focusing screens, and the ground glass can be very hard to focus accurately in low light conditions. Even focusing on subjects after the sun dips below the horizon can be quite difficult with this camera.
One of the biggest surprises to me was the amount of extra gear required to use this thing. You learn quickly that this camera is very different from most SLR's, and there are a lot of extra bits and pieces you'll want to get. The first and most important is a tripod. Trust me, you really will want one at some point. Because the depth of field is so shallow on medium format cameras, I often find myself using shutter speeds as low as ~ 1/15 of a second even in broad daylight to get everything in focus. Make sure you get a set up capable of holding at least 25-30 lbs, since manufacturers dramatically overrate their weight capacity. It doesn't have to be very tall, especially if you use the waist level finder. I personally use a Sirui T-2005x travel tripod and a vanguard ball head, and it works out fine despite it being on the small side.
The Second essential piece of gear is BOTH a cable release AND a soft shutter release. The latter is absolutely critical if you're going to handhold the camera, because the awkward way you hold the camera tends to amplify any shakiness in your hand while taking the photo, and it will help to keep motion blur to a minimum. A cable release is a must have for tripod work, because even on a sturdy tripod mirror slap can cause some motion blur. When using it on a tripod I always use a cable release so I can trip the mirror and shutter separately.
The last essential for using the RB67 is a light meter, because it doesn't have one built in. If you want, you can use an app on your smartphone for this, but I prefer to use a dedicated meter(a Gossen Pilot) and it works great. To go with your meter, you'll want some kind of table with the reciprocity failures for your film stocks of choice. If you're using a phone as your meter then just keep them on there, but if not(like me), I like to keep the data tables in the front of a "field notes" notebook that stays in my camera bag.
While they aren't absolutely essential, you will likely want spare film backs, viewfinders, etc, so keep that in mind when buying your camera as well. All in all, tripod and head aside, you should budget for ~ $100-150 in extras for your RB67 camera. Even still, this camera is significantly less expensive than many cameras like it such as Hasselblads, medium format rangefinders, and the RB67's younger brother the RZ67 series.
Despite what some might consider to be a lot of downsides, the photos this thing takes make it more than worth the trouble. The Image quality of 6x7 negatives is incredible, and the Mamiya Sekor lens lineup for this camera is one of the best of all the medium format camera systems. Even the original lenses like the single-coated 90mm Sekor (non-c) lens that I use is incredible. When viewed under a loupe, I am always stunned by the amount of detail in these negs, and with proper scans and printing, I doubt you would have any trouble making poster-sized prints with the same sharpness and image quality as an 8x10.
IQ aside, the photos from this camera have a lot of aspects that I prefer to other cameras, aesthetically. One of the reasons I wanted a 6x7 camera was for the 4x5 aspect ratio, and I MUCH prefer it to the wider 2x3 ratio of 35mm and 6x9 cameras. The bokeh this thing is capable of is great as well, and when focusing up close for tight headshots and macro photography, you will be blown away by the razor-thin DOF that even the wider lenses with a max aperture of F/3.5 produce. Short of going to large format, I doubt you will do much better IQ-wise, even with newer cameras and glass, and in my opinion the RB67 is one of the best portrait cameras of all time.
While I love to rip on this cameras weight, size, and slow learning curve, it is honestly one of my all time favorite cameras, right up there with my Nikon F3. Since getting it, I have felt little need for any other camera, and I could potentially see it becoming my only camera if push came to shove. I don't think it is a camera for everyone, but if what I've outlined here appeals to you, I think you'll really enjoy using it.