Medium format has traditionally referred to a film format in still photography and the related cameras and equipment which use this film. Generally, the term applies to film and cameras used to produce images larger than the 24 by 36 mm of 135 film, but smaller than the 4"×5" size, which is considered to be large format.
In digital photography, medium format refers either to cameras adapted from medium format film photography uses, or to cameras making use of sensors larger than that of a 35 mm film frame. Often, medium format film cameras can be fitted with digital camera backs, converting them to digital cameras, but some of these digital backs, especially early models, use sensors smaller than a 35 mm film frame. As of 2006, medium format digital photography sensors were available in sizes of up to 36 by 48 mm, with 39 million pixels for use with commonly available professional medium format cameras. Sensors used in special applications such as spy satellites can be even larger, but are not necessarily described as medium format equipment.
In the film world, medium format has moved from being the most widely used film size (1890s through 1950s) to a niche used by many professionals and some amateur enthusiasts, but one which is still substantially more popular than large format. In digital, medium format is a very expensive option, with typical brand new all-digital medium format cameras retailing for $10,000 (Mamiya ZD) to $32,000 (Hasselblad H3D) in 2008, though older and used equipment can be substantially cheaper.
While at one time or another a variety of medium format film sizes were produced, today the vast majority of medium format film is produced in the 6 cm 120 and 220 sizes. Other sizes are mainly produced for use in antique cameras, and many people assume 120/220 film when the term medium format is used.
In general (consumer cameras, as opposed to specialized industrial, scientific, and military equipment), the more cameras sold, the more sophisticated the features available. As a result, medium format cameras made since the 1950s are generally less automated than smaller cameras made at the same time, having high image quality as their primary advantage. For example, autofocus became available in consumer 35 mm cameras in 1977, but did not reach medium format until the late 1990s, and has never been available in a consumer large format camera.
Compared to 35 mm, the main drawbacks are accessibility and price. While 35-mm cameras, film, and photo finishing services are generally widely available and cheap, medium format is usually limited to professional photography shops and can be prohibitively expensive, especially for digital medium format cameras.
Most large format film is sheet film, that is, film where each picture is on a separate piece of film, requiring that the camera be frequently reloaded, usually after every picture, sometimes using magazines of up to five pictures or reduction backs that allow multiple pictures on a single sheet of film. Medium format sheet film was produced for some cameras, but these cameras tend to be smaller, lighter, and easier to use than large format gear. Sheet film was never commonly used in cameras smaller than medium format.
Film cost per exposure is directly related to the amount of film used, thus, the larger the film size, the more expensive each picture will be. An 8"×10" large format negative is far more expensive than a 6×6 cm medium format picture, which is substantially more expensive than a frame of 35 mm film.
Thirty-five mm cartridges are generally easier to load and unload from a camera than medium format rolls. A 35 mm cartridge is placed inside a camera, and in most motorized cameras this is all that is needed; the camera loads the film, and rewinds it into the cartridge for removal. Far fewer medium format cameras are motorized, and medium format roll film does not have sprocket holes, so loading often requires that marking on the backing paper of the film be lined up with markings on the camera, and on unloading, the backing paper must be carefully secured to protect the film from light.
All medium-format cameras mass produced today (as of 2008) use the 120 film format. Many also can use the 220 film format, which is twice as long and hence allows twice the number of exposures. 120 and 220 film is still almost as available as 35 mm from specialist shops.
This film is shot in a variety of aspect ratios, which differ depending on the camera or frame insert used. The most common aspect ratios are 6×6 cm (square) and 6×4.5 cm (rectangular). Other frequently used aspect ratios are 6×7 cm, 6×9 cm, and 6×17 cm panoramic. The 6×4.5 cm format is usually referred to as "645", with many cameras that use this ratio bearing "645" in their product name. Cameras that can switch to different aspect ratios do so by either switching camera backs, by using a frame insert, or by use of special multi-format backs. All of these dimensions are nominal; actual dimensions are a bit different. For example, 6×7 cm might give an image on film that is actually 56×70 mm; this enlarges exactly to fill an 8×10 sheet of paper. Another feature of many medium format models is the ability to use Polaroid instant film in an interchangeable back. Studio, commercial and architectural photographers value this system for its ability to verify the focus and exposure.
Many professional medium format cameras are "system cameras", which means that they have various interchangeable parts. Like most 35-mm SLRs, these cameras usually support different lenses, but in addition it is also standard for medium-format system cameras to support different winding mechanisms, viewfinders, and camera backs. This flexibility is one of the primary advantages of medium format photography.
This market began in 1992 when Leaf Systems Inc. released their first digital camera back, named, fittingly enough, the "DCB". By the late 1990s, there were a number of companies producing backs of various types.
In the 2000s, the number of vendors of both high-end medium format camera systems and digital backs began to decrease. The power of digital SLRs cut into the sale of film-based medium format systems, while the tremendous development expenses for medium format digital systems meant that not all vendors could profitably compete. Contax and Bronica ceased production of cameras, Kodak stopped making their DCS series of backs, and camera and back manufacturers began to integrate.
Camera maker Hasselblad merged with digital imaging firm Imacon and partnered with Fuji to design and produce a new line of digital-friendly medium format cameras, the H-Series. Since the manufacturer will sell digital backs integrated with the camera, other makers of digital backs are far less likely to be able to sell backs for this camera, and this partnership is the clear market leader.
Camera maker Mamiya has developed the Mamiya ZD back, but also announced a partnership with back maker Phase One. Camera maker Sinar was taken over in stages by the digital cameraback manufacturer and developer Jenoptik and partnered with Rollei for the development of the Hy6 medium format camera systems.
The Leaf Aptus 75S digital back offers 33MP resolution, with shooting speed of 50 frames a minute. In early 2006 Hasselblad (H2D and H3D) and Phase One (P45) released a 39 megapixel back, the highest resolution single-shot digital backs to date. Phase One continues to dominate the high end non-interpolated imaging with the largest market share. Line up of scan backs like the PowerPhase FX+ through to the latest P45+ which also has live image focusing.
While most professional medium format cameras are very expensive, some inexpensive plastic imports, such as the Chinese Diana and Holga, are gaining in popularity, particularly with toy camera enthusiasts. Many of these cameras are sold though the Austrian Lomographische AG. Due to the poor quality of the cameras, the exact image captured on the negative is somewhat random in nature. These cameras often have plastic lenses that offer poor or uneven focus, light leaks that oddly colorize an image, extreme vignetting, and a multitude of other "flaws" that are generally undesirable to photographers. While these elements certainly are "flaws" in camera design, they can produce interesting, artistic, or enjoyable results. Because of the popularity of lomography and toy camera culture, medium-format photography has seen a resurgence with amateur photographers. Lomography detractors point out that twin-lens reflex cameras (TLRs) and folders without the distortion and light leaks can be had on the used market in the same price range.
The Chinese Seagull TLR and medium-format cameras from the former Soviet Union such as the Russian Lubitel and somewhat better made Ukrainian Kiev-Arsenal 60 and 88 are also available at moderate prices. These cameras can deliver quality images, although the lenses and camera bodies are not at the level of those from Swedish, German and Japanese manufacturers.
Used folding cameras, TLRs, and box cameras are also a cheap option to shoot medium format. Many U.S.-made folders, including most of the mass produced Kodak folders use the discontinued 620 film requiring the user to respool 120 film.
Additionally, most large-format cameras can, with the use of roll-film adapters, use medium-format film.
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