Most cameras are easy to pigeonhole - 35mm rangefinder, medium-format SLR, large-format view camera, or whatever. One type of camera, however, generates more confusion - and contention - about it's place in the grand scheme of things than any other.
I speak of 2-1/4 by 3-1/4 (aka 6x9cm) "baby" press cameras. Older "baby" Speed Graphics are perhaps the most common and best-known, but there are a dozen or so other models that show up relatively often. With the exception of Linhof's technical cameras - which were never true "press" cameras in the strictest sense - no two people seem able to agree on what to consider these things.
All can be fitted - if you know the tricks - with 120 rollfilm backs, which seems to make them clearly medium-format cameras. Yet your typical Hasselblad user isn't going to know a thing about movements - the shift, rise, and tilt available on most of these cameras. They were designed to be used with sheet film, and while they share a clear kinship with their larger 4x5 inch brethren, large-format users - in addition to often dismissing all press cameras, regardless of size, as not having enough movements to be "real" large-format cameras - are generally raving size queens, and don't consider 2x3 inch negatives "large".
Thus we have the humble baby press cameras, the unloved illegitimate bastard children of large-format field cameras and old rollfilm folders, about which this is the first of several pages on this site. Smaller and more "limited" in features than one, and freakishly large, heavy,and complicated compared to the other, they're overlooked, ignored, or dismissed by most.
They don't know what they're missing, though.
In terms of performance, to be absolutely frank, one baby press camera is much like any other - that is to say, they're all, if in good working order, capable of producing excellent results, and are able to let the photographer explore medium format to it's absolute fullest. The differences are slight, and mostly irrelevant, but I hope to explore three or four of the most common of these cameras in depth, as information about them - particularly second- or third-hand - is often, at best, incomplete. Most will be found with a lens in the 101mm to 115mm range, usually f/4.5, which is "normal" for 6x9. Fitted with a 6x6 rollfilm back, this is an excellent length for portraiture.
A press camera - of any size - is a jack of all trades. On a tripod, they make excellent landsape and pictoral cameras and have more than enough movements for the vast majority of reasonable applications. Handheld, they're excellent - and fun! - reportage cameras, if you can live with the slow lenses and shallow depth of field inherent in larger formats. In the studio they are excellent for portraiture, as already mentioned, and readily impersonate ridiculously expensive technical cameras.
In their day, these were professional cameras, well built - even overbuilt - and designed for the rigors of daily use and abuse. There were no cheap "WalMart Special" press cameras, no "entry-level consumer" ones; the few "store-brand" models were just rebadged first-name cameras (Burke and James of Chicago made all of Sears' press cameras, for instance, and except the the nameplates they're absolutely identical to B&J's own cameras of the same era). Even the least expensive lenses - f/4.5 triplets like Optars, Trioptars, Raptars, and Velostigmats - were excellent performers then and still good today. Some - like the relatively common Kodak 101mm f/4.5 Ektar - are still considered by many to be one of the, if not the, best lenses of their focal length and coverage. As glass plates fell out of fashion, a lot of photographers back then - and a lot of photographers today - fit to their press cameras excellent lenses off of old plate-only view and field cameras, such as Zeiss' 12cm, f/4.5 Tessar.
Much as with any other camera, a press camera is a just a light-tight box (and bellows!) with a lens, shutter, and means of exposing film. There are minor differences between them all, of course, but in practical use almost none. Unless you have some sentimental, aesthetic, or personal reason for wanting a particular marque or model of 2x3 camera, you'd do best to look for a specific lens - such as a Tessar or Ektar, perhaps - or a specific shutter (perhaps one with X-sync for electronic flash). In the absence of other concerns, shop on price and condition, particularly that of the bellows. A camera that rode around in the trunk of a reporter's or policeman's car for a decade may be well battered on the outside - usually nothing a good cleaning and some leather conditioners can't fix - but the condition of the bellows - hopefully protected from wear and tear - are far more important than the body covering. A new 2x3 bellows costs around $150 USD in 2006, which is as nearly as much as, and often more than, the camera is likely to cost.
One of the most common - and most affordable - 2x3 press cameras is the "Pressman C", made by the Busch Precision Camera Corporation of Chicago. A wood-and-metal camera wrapped in black leather, it looks much like any other classic press camera. Unlike the Speed Graphic, it has no focal-plane shutter, and no Pressman was ever made with a Graflok back, the tres-desirable rear end that allows the easy attachment of rollfilm holders and the like. These two deficiencies keep it's selling price under - often well under - $200, with lens, shutter, and accessories.
They're not really deficiencies, though, and the camera is one of the best bargains around.
A lot of people are really hung up (no pun intended) on the Speed Graphic's focal-plane shutter. Thirty-five years after they were last made, though, the huge fabric shutters are nearly impossible to repair. Even when working, they were - and still are - frequently stripped out of the bodies to eliminate their considerable weight. With the demise a decade ago of the process camera, there are no modern shutterless lenses that require the camera to have it's own shutter, and very few of the vintage "barrel" lenses are really suitable for use on 2x3 cameras. By not buying a Speed Graphic, you're saving a fair bit of money, and losing a heavy, unnecessary shutter than is frequently irrepairable.
Graflok backs were found on some, but not all, postwar Graflex cameras, in 2x3, 3x4, and 4x5 sizes. They're a pair of sliding metal bars that lock accessories - like a Graphic rollfilm holder - onto the camera. A lot of people insist they're the only practical way to use rollfilm with a 2x3 camera. Bullshit; it's just not so.
The Busch Pressman has a ground-glass spring back, like most cameras of it's type. It's attached to the camera with two screws. Thirty seconds with a screwdriver, and you've got a backless camera. If you have an elderly Suydam rollfilm holder, it can be attached very easily, either temporarily or semi-permenantly, both of which are traditional ways of using these cameras with rollfilm. Indeed, Suydam used to make complete replacement backs for 2x3 Pressman cameras, with removable ground glass, though they're not terribly common. As with the slightly drastic measure of glueing a rollfilm back to the camera, if your camera has a coupled rangefinder that's in correct alignment, you can focus that way.
That is a traditional and historically-correct way of doing things, but if you do so, you'll have created a basic press camera - a folding 6x9 (or 6x7,or 6x6, depending on your rollfilm back) camera significantly larger and heavier than your basic 6x6 to 6x9 folding camera. Rangefinders can't readily be used with multiple lenses, and while you can mark the camera bed with focussing scales for several lenses, scale-focussing is never as accurate as other methods, and cameras like the Pressman don't facilitate the rapid swapping of lenses, or at least not to the extent of most 35mm systems, and many other medium- and large-format cameras.
To take advantage of the extra weight and features you're carrying around, you need to focus on the ground glass. With sheet film, it's easy; focus on the glass, then slip a film holder under the glass. With rollfilm, you need to remove the ground glass and mount the holder. The Graflok back is certainly the most convenient way of doing this, but there are other options, besides those I've already mentioned.
The easiest is the purpose-made one; Graflex and probably other companies made "spring kits" that could be installed on the back of a camera, and would allow Graflok accessories to be mounted. Nowadays they're extraordinarily difficult to find; I've seen exactly one.
A brief look at one was all it took, though. A little creativity, three hand tools, some junk mail, and fifteen minutes are all that is required to reversibly modify a Pressman C so that it can be used with both the ground-glass back AND rollfilm holders, conveniently, reliably, and safely. If you have a Graflok-compatible rollfilm back (either a Graflex, a Mamiya RB, a Linhof, or a Horseman) and a Pressman, taking the spring back off and holding the rollfilm back in place should suggest several different ways of installing it.
When used with rollfilm, a camera like the Busch Pressman gives you the best of all worlds - modest price, weight,and size, coupled with interchangeable lenses, a huge negative (as I've said elsewhere, a 6x9cm transparency is a joy to behold), and the ease and affordability of 120 rollfilm, in formats from 6x4.5 (the RB67 "645" back) thru 6x9.
But that's true of pretty much any 2x3 press camera. If you're considering one, the distinct advantages of a Pressman are as follows: Firstly, they are extremely well made; perhaps not up to Linhof or Alpa standards, but Busch took the "precision" part of their name seriously, and it shows. Compared to cameras like Burke and James' "Watson", the build quality of a Pressman is outstanding. Second, the rear plane of the camera - what the film holder, ground glass, or rollfilm back seats against - is a thick slab of aluminum on the Pressman, pretty well eliminating worry about wear or - horror! - warpage. Thirdly, if you get a later Pressman - one with a black lens standard and four small screws attaching the lensboard - the lensboards are nearly as simple as they get, and can be easily fabricated by anyone reasonably competent with tools. This isn't necessarily the case for the special aluminum boards required for the earlier version (reproductions of which are still available, albeit for close to $50 USD), or those used by cameras like Graflex's Century Graphic.
To be fair, the factory lenses on Pressman aren't always top-of-the-line. Truth be told, though, even the lowliest Wollensak Raptar or Optar is a perfectly good lens, and great lenses - like Kodak's 101mm, f/4.5 Ektar - don't have to cost a fortune. (The Ektar, in a Supermatic shutter, is a common, sub-$100 item, even in good condition.) It's six-plus inches of bellows draw and drop-bed allows the use of a wide assortment of lenses, both vintage and modern.
The Pressman C is inexpensive, well-made, and probably the most common non-Graflex 2x3 camera out there. Further, with the exception of the focal-plane shutter of the Speed Graphic, it can do everything any other 6x9cm press camera can do. A "stripped-down" Pressman, with no rangefinder, no optical viewfinder, and no handle, measures about 4-7/8 inches wide (plus a half inch or so for the focus-lock knob, which protrudes from the right side of the bed), 5-1/2 inches tall, and about 3-1/8 inches deep when folded. The handle adds a quarter-inch or so of width, the viewfinder perhaps three-quarters of an inch in height, depending on model, and the rangefinder adds about an inch more to the width (or a half-inch beyond the focus-lock).
The rangefinder and viewfinder were very much optional accessories, but it might seem odd to some to give dimensions without the handle, which was a standard part of every Pressman. Sure, the old handles have mostly fallen apart, but replacements are easy enough to make or purchase. Well, the reason you might want to remove the handle is simple - the second tripod socket is between the two handle brackets, and if your tripod head or quick-release plate is more than 2-1/2 inches across (i.e. has a radius greater than 1-1/4 inch), the bottom handle bracket is going to be in the way. If you want to shoot vertical images with this camera, it's much easier to use the side tripod socket.
A note about viewfinders: Busch made a fairly nice viewfinder for the Pressman. It's bright and contrasty, and has (impossible to find) interchangeable masks for different focal lengths. It's really quite beautiful. It's also made of phenolic resin (bakelite), and is badly designed. The popular Graflex "tubular viewfinder", cast from magnesium (no, really), is often found on Pressman cameras, and is not only significantly better designed, but easier to use, though the Busch is - very arguably - more accurate. You can often find the Graflex viewfinders for sale cheaply - but make sure they include the mounting plate and screws, or you're going to have to get creative.