So what is it and why bother in the first place? Medium-format is a term used to describe the range of neg and trannie sizes, known as formats, available on 120/220 and 70mm roll-film. The range is large, going from 645 (6cm x 4.5cm giving 15 exposures on a roll of 120), through 6x6 (6cm x 6cm, also known as 21/4sq, 12 exposures), 6x7 (10 exposures), 6x8 to 6x9. The panoramic formats 6x12, 6x17, 6x18 & 6x19, although on 120/220, are not usually called medium-format. Not all cameras will accept 220 roll-film, a double-length version of 120 made possible by replacing the light-proof backing paper with short paper leaders taped on both ends. Even less accept 70mm film, which looks like big 35mm film. Not all films that are available in 35mm are manufactured in 120, even less in 220 and 70mm, but this tends not to be a big problem.
The main reason for using medium-format is that the increased film area used for each shot increases the number of halide grains that make up any area of the image, for any given film. Compared with the film area of a 35mm frame, 645 is approximately 3x, 6x6 4x and 6x7 4.9x. So for any given film and print size, whether B&W or colour, the size of the grain in the finished print is reduced and gives smoother tones. The larger the format, the greater the effect, whether negs or trannies. Although medium-format trannies are not normally projected as slides. They do look stunning when projected, but the cost of the projectors is shockingly high and rules it out for most people. On a light-box, medium-format trannies are easier to view and the higher quality makes them preferred over 35mm for many magazine, book and other uses.
I know this will probably upset those of you with 645 cameras (and their manufacturers) and I do know there are a number of excellent 645 camera systems about, that the kit tends to be cheaper than the larger formats, that some offer more in the way of automation and that 645 is usually seen as the "next step up" from 35mm, but I don't like 645. In my experience the difference in quality between 645 and 6x6 is significant. Perhaps my objections are unrealistic, coming from routinely printing large prints at work, e.g. 20ftx16ft. Even though the 645 format closely fits a 20x16 print, a 6x6 trannie cropped down always seems to give a better result when it's feet not inches - and a 6x7 even more so.
medium-format cameras fall into four main groups; single lens reflexes, twin lens reflexes, range-finder and the more specialised cameras with scale focusing on the lens or a ground glass screen. All have their own advantages and disadvantages. The SLRs are the most advanced, particularly in 645, some offering facilities such as auto-focus, auto-exposure and motor-wind. All current 35mm SLRs use a focal plane shutter, which is fitted in the camera body and travels close to the surface of the film. A between-the-lens, or blade, shutter is fitted into the lens. Both have advantages and disadvantages. A focal-plane shutter is very useful with interchangeable lenses, since it automatically covers the film between exposures and when changing lenses, and no shutter and linkages are needed in the lens, reducing the cost. The main drawback of focal-plane shutters is that, because they work by one fabric or metal blind uncovering the film and then a second following to cover it back up, they can only synchronise with electronic flash up to the last shutter speed that leaves the film completely exposed. The maximum flash sync speed of most modern 35mm SLRs is around the 1/250th of a second mark (this excludes the "long-burn" system flashguns). Because of the much larger size of the focal-plane of a medium-format camera, the maximum flash sync speed tends to be much lower, round a 1/30th. This can cause problems with flash. In the studio, when using wide apertures the tungsten modelling lights can begin to influence the exposure, causing problems with overexposure and colour casts on colour film. Out in daylight, a slow maximum sync speed makes it difficult to use fill-in flash, a technique that can make an enormous difference in strong sunlight and can also be used as a creative tool. (See TechTalk 12.) The between-the-lens shutter, on the other hand, can sync with electronic flash at all speeds, but is normally limited to a top speed of 1/500th, one is needed in every lens, with linkages to the camera body and a capping shutter is needed in the camera to protect the film between exposures (due to the shutter needing to be held open for viewfinding) and during lens changes. This makes things more expensive. Myself, I prefer the between-the-lens shutter, for its flexibility with flash. Some cameras offer both. Hasselblad allows lenses with between-the-lens shutters to be used on the focal-plane bodies and the Pentax 6x7, now available in a more modern Mark 2 version, has a 165mm between-the-lens shutter lens, as well as a, no longer manufactured, 90mm. Although these Pentax bladed-shutter lenses give more flash flexibility, the way they operate (certainly on the MK1 body) is via the aperture stop-down linkage, need the focal-plane shutter set to 1/8th or slower and to be manually cocked before each exposure. If they are not manually cocked, they remain open and the film gets the exposure that the focal-plane shutter is set to. Result, blurred and severely overexposed negs or trannies (been there, done that and didn't like it). The Pentax 6x7 is an exception to the general rule of medium-format cameras, being designed more like a 35mm SLR and easily used with an eye-level prism finder, but no interchangeable back. Most medium-format SLRs have interchangeable backs, sometimes called magazines, that can be removed, either to be replaced with a different back, e.g. to allow Polaroid film to be used for test shots or to allow a different format to be used (e.g. 645 instead of 6x6), it also means films can be swopped mid-roll allowing shots to be alternated on two or more different films, and several backs can be loaded before a shoot and changed faster than loading a new film (faster even than loading a 35mm camera). If an assistant is used, the backs can also be reloaded during the shoot. Eye-level prism finders are available for most medium-format SLRs, not just allowing the camera to be used at eye-level, but turning the normally reversed left-to-right viewfinder image, back to normal. However, because they are so large, they tend to be quite expensive.
Twin-lens reflexes have the viewfinding and taking functions handled by separate halves of the camera, rather than being combined as in an SLR. The bottom half of the camera houses the film plane and the taking lens and shutter (always a between-the-lens type), the top half houses the mirror, viewing lens and focusing screen. Because the mirror doesn't need to move out of the way, nor does the shutter and aperture need to close, to make an exposure, the whole camera is much simpler - and therefore cheaper - to make. Drawbacks with TLRs are mainly that they only come in 6x6 format, since it would be hard to use the camera turned on its side, the lenses are not interchangeable, neither are the backs and because the viewing and taking lenses are separated by a small distance, the views seen are slightly different. This gets worse the closer the subject is to the camera and leads to a problem known as parallax error, where the views are different enough to cause cropping of the subject at the top of the frame and inclusion of unwanted subject at the bottom. An exception to some of the above drawbacks is the Mamiya TLR range, which has interchangeable lenses and a parallax indicator coupled to the focusing system. TLRs were very popular from the 1940's through to the 1960's, with amateurs and professionals alike, until being ousted by the 35mm rangefinder and SLR. Many can still be picked-up second-hand quite cheaply and, as long as they are in good working condition, is the cheapest way to start in medium-format. There are still professional photographers today doing weddings and portraits on old Mamiyas and Rollis, which produce prints indistinguishable from an expensive modern SLR.
Rangefinder medium-format cameras offer some of the ease of use of eye-level SLRs, but at lower cost and lighter weight. Perhaps the ideal "stock shot" travel camera, they are available in 6x6 and 6x7, with interchangeable lenses. No interchangeable backs and some of the lens options need an additional accessory-shoe viewfinder, but offer the best compromise in speed of use without going 645 automatic.
The final category is the more specialised use cameras that offer some of the movements of a large-format camera, such as shifts, with a rollfilm back. Lighter, smaller and easier to use on location than large-format, they are mainly intended for architectural photography. There are also medium-format cameras with interchangeable scale-focused lenses and eye-level viewfinders, sometimes known as press cameras because they were designed as an alternative to the large-format press cameras of yesteryear, most notably the Speed Graphic. Only available second-hand and usually more expensive than TLRs, they do offer an alternative to the SLR with eye-level finder.
In my view, the biggest advantage of moving from 35mm to medium-format is the way that it encourages you to think a lot more about what you are doing and why you are doing it - before you press the shutter button. Less exposures to a roll and a need with many cameras to use a handheld light meter and manual focusing, slows you down and gives you time to think, rather than just motor-driving through film, hoping that something will come out.
This brings me to an alternative to "moving-up"; Kodak Technical pan film is available in 35mm and is extremely fine-grained, capable of resolving more detail than any 35mm camera lens. Actually a high-contrast film, similar to lith film, it can be developed in a very low-contrast developer (Kodak make and recommend Technidol (info sheets available from Kodak or via Kodak website - either go through professional photography or do a search) - others are available - or make your own POTA) that give a "pictorial" range of tones. It is a very slow film, ISO 6 to 25, depending on development and lighting (it's more sensitive to red light than ordinary pan film), so it encourages you to use a tripod, meter carefully and think before pressing the button. And whatever format you are using, that is one of the biggest ways available for improving your photography.
© Barry Leighton FRPS