|The Pentacon Six System
Medium Format Camera Specifications
The very first photographic images were genuinely unique, in that only the original image was produced on whatever material had been made sensitive to light. In this image, the light areas of the subject were dark and the dark areas of the subject were light. The only way of producing copies of the image would be to photograph it and thus produce one copy. However, the sensitivity of materials used was so low that even photographing an original image was uncommon, as exposures needed to be hours long.
The image produced was also the size of the sensitized material and not only could copies not be made (other than by photographing the image), the size could not be changed. The camera was therefore built to the appropriate size to hold the sensitized material, and if a large image was desired, the camera had to be large, too.
“Negatives” and “Positives”
These two limitations were overcome when the English inventor William Henry Fox Talbot created a two-stage process in which he called the original image “the negative” and from this he made a copy that he called “the positive”. This was in the second half of the 1830s. His invention made two things possible:
Cameras could now be smaller than the intended image size. In spite of this, limitations in the grain structure of the recorded image and in the resolution of the lenses used meant that for larger images, larger camera formats were still desired.
Throughout the rest of the 19th century, cameras with a wide range of formats were made. Various sensitized materials were used, including paper, but very soon, manufacturers settled on the use of sensitized sheets of glass to record the negative image. These sheets were known as “glass plates” and each plate had to be stored in a light-proof container until the photographer was about to take the photograph.
According to the website “Plate sizes”, accessed on 6.9.21. here, the standard plate size, known as “Full Plate”, had the dimensions 6½" × 8½", equivalent to 216mm × 165mm.
There was constant pressure to produce cameras that were smaller and lighter, resulting in other sizes, including “Half Plate” (4¾" × 6½" / 120mm × 165mm) and “Quarter Plate” (3¼" × 4¼" / 83mm × 108mm).
From 1888 onwards, George Eastman was producing small cameras in which the sensitive material used was a roll of sensitized film. For more on this, see the Wikipedia “Kodak” article, accessed on 6.9.21. here. When individual sheets of film are used in appropriate cameras, the film is often referred to as “cut film” or “sheet film”.
Film weighed a lot less than glass, took up less space and was less fragile: if you dropped a film, it didn’t break! However, early films tended to curl, which would result in parts of the image being out of focus, so glass was preferred for maximum image sharpness.
Rolls of film had another advantage: replacing the exposed film frame with an unexposed frame was much easier and faster than covering a glass plate or sheet film, removing the holder, putting a new holder into the camera and removing the “dark slide”.
The website “35mm film”, accessed on 6.9.21. here, states “The 35mm format for film was first developed on an experimental scale in Thomas A. Edison's laboratory more than 120 years ago. Edison's associate William Dickson created devices for photographing and viewing moving images on film loops 35mm wide, for which Edison filed a patent in 1891.” The film was run vertically through the ciné camera and image size was 24mm wide × 18mm high. The rest of the film width was occupied by sprocket holes running along both sides of the film, just in from the edge of the material.
This was soon adopted for “stills” photography, first running vertically, but soon with cameras in which it ran horizontally. With the development of cameras in which the 35mm film ran horizontally, the frame was generally set at double the image size used for ciné cameras, resulting in the format 36mm wide × 24mm high. In the course of the 20th century, this became known as “full frame”, but in the early years it was known as “miniature film”. The one camera brand that made the 36 × 24mm format popular in the 1920s was Oskar Barnack’s Leica camera, manufactured by Ernst Leitz Optische Werke in Wetzlar and launched at the Leipzig Spring Fair in 1925. (See here, accessed on 6.9.21.)
By 1932, a major 35mm camera competitor for the Leica was the Contax 35mm rangefinder camera. See more information here and on the subsequent pages.
From the late 1950s onwards, various cameras were manufactured that used the original ciné format of 24mm × 18mm. These were then called “Half Frame Cameras”. Pentacon made the Penti and the Penti II, but the most famous “half frame” cameras came from Olympus, many of them with the name “Pen”. At the time of writing (6th September 2021), there is some information on these cameras here.
By the late 1920s there was a range of camera sizes using either glass plate or cut film, and popular sizes included:
Larger sizes were also common, including
some much larger sizes. Sometimes the supporting
material was glass plates, sometimes it was cut
film. The metric sizes in this table are not a
conversion of the “imperial” sizes given in the
left-hand column, merely common sizes that were broadly
Medium Format Cameras
We can see that with the large cameras that take glass plates or sheet film at one extreme and “miniature” format cameras at the other, it was perceived that there was space for something between the two extremes, a “Medium Format” that would combine some of the advantages of each extreme:
Medium Format Frame Size
The format adopted by Paul Franke and Reinold Heidecke for their Rolleiflex camera was a nominal “6×6” cm square on 120 film, which provided 12 exposures. This format was also adopted by other cameras in the subsequent decades, including a range of Single Lens Reflex cameras that started to appear in 1932 with the Noviflex. See more information on this camera and the ones that were inspired by it in the History Section of this website, especially here and on numerous subsequent pages.
In “Praktisix Buch”, Dr W. G. Heide states, “The PRAKTISIX is built for 120 Roll film.” (p. 55) Translation by the author of this website. (Original German: “Die PRAKTISIX ist für den Rollfilm Nr. 120 ... gebaut.”
For more information on this book, see here.Heide continues,
The size of the film gate for the Praktisix is identical with its size in the Pentacon Six. We note that Heide describes the image frame dimensions as “approximately” 5.6 cm (56 mm) × 5.6 cm.
I have measured the size of the image on the film that is produced by the Pentacon Six, and have found that it is fractionally under 56mm, being in fact 55.5 mm or 55.45 mm, as far as I am able to measure. However, we must recall that the manufacturer did not intend the whole of this image area to be used.
As we have described elsewhere on this website, for the Hasselblad medium format cameras launched after the Second World War, the image frame dimensions were specified as “54mm × 54mm”:
“Thus, Hasselblad Inc’s Technical Director (in the USA), Ernst Wildi, writes in “The Hasselblad Manual, 2nd Edition” (1982):
“The 2¼ in square
Exact image size: 54 ×54 mm” (p. 3)”
Likewise, according to Lothar Braas in his book “Das Kiev Mittelformathandbuch, Band 1: Die Kameras”, the usable area of a “6×6” frame is 54mm × 54mm.
For a series of lens tests for this website I used a major processing lab in London to develop my film and produce prints, and their enlarger mask is 53mm × 53mm, according to my calculations based on the prints they supplied.
Likewise, the image area visible in a slide mount is of necessity less than the total image dimensions on film, in order to ensure that no light gets round the edges of the image area and degrades the quality of the projected image on the screen. So it does indeed seem that for the “6 × 6 cm / 2¼" square format”, the usable image area is intended to be between 53mm × 53mm and 54mm × 54mm.
“Medium Format” Digital Cameras
In the 21st century, various digital cameras boast of being Medium Format Cameras. However, this is never “6×6”, nor even 53mm × 53mm. Thus, the Fujifilm GFX50 and GFX100 cameras have a sensor that is 44mm wide × 33mm high. There are some “Medium Format” digital cameras with sensors larger than this. However, in 2021 the term “Medium Format” now appears to be applied by manufacturers to any digital camera with a sensor that is larger than the “old” 35mm format “full frame” of 36mm × 24mm. The quality of the images obtained can be excellent, but it is good to be aware that the definition has changed. Even if the quality is more than acceptable, one must remember that if one uses medium format lenses from analogue cameras on these new “Medium Format” digital cameras, the subject area covered will be much smaller than with the original analogue camera.
For long lenses, this can be a bonus: the lens appears to “magnify” more than when used on an analogue Medium Format camera.
But for wide-angle shots, this is a disadvantage, as the wide angle lens covers a narrower angle than when used on a genuine Medium Format film camera.
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© TRA September 2021