Introduction: Graflex, Mamiya RB67, Horseman, Mercury
No medium format removable back standard has been more influential than Graflok 23. It was the first medium format back protocol to gain sufficiently widespread adoption to be considered a “standard” at all. It was and remains the only multi-brand 6×9 format standard for removable backs. It drove the adoption of removable roll film backs for decades of influential Graflex cameras in the postwar period, such as the Crown and Speed “Baby Graphics,” the Century Graphic, and the influential Graflex XL system. It is the standard utilized by perhaps the most influential medium format portrait camera in the history of photography: the Mamiya RB67. It was the standard adopted by Horseman for their high-end medium format view cameras for decades (until they stopped making view cameras entirely). It is the default medium format back standard adopted by the Mercury Open Camera System, opening the standard to a new generation of photographers and camera designers. Until now, however, there has been no comprehensive repository of information about the array of backs that have been released by various manufacturers for this standard. Graflex, Mamiya, and Horseman users have all had to make due with web resources devoted only to their own brand, which are necessarily incomplete (and often quite inaccurate).
This Guide is the result of years of research, testing, collecting, photography, and design, largely driven by the Mercury project. It is divided into two Parts: a history of the standard, including the many products made for it, in chronological order, and a guide to each back, organized by format. New users or prospective purchasers are encouraged to start with Part I; experienced photographers may wish to jump straight to Part II.
Part I: History of the medium format Graflok back
Graflex invented the 2 x 3 “Graflok” back at the same time as their 4×5 counterpart, in 1947. An update and upgrade from their earlier “Graphic” removable back from their reflex cameras, the Graflok standard allowed accessories like roll film backs to be easily attached and detached from the back of cameras, without needing to fit underneath the spring backs of most competitor’s cameras (sheet film holders are designed to slip under these spring backs; most roll film backs were too thick to do so). All “baby” Crown and Speed Graphics from this period onward incorporate it. At the same time, Graflex released their well-known line of roll film backs: the “22” 6×6 and the “23” 6×9. Both backs accept rolls of 120 film. The “22” exposes a frame approximately 2″ x 2″ (actually a bit larger, but Graflex liked nice even numbers in their product names). The “23” exposes a frame approximately 2″ x 3″. This is how the Graflok 23 standard gets its name: 2″ x 3″ was considered the native (“full frame”) exposure size for this back standard.
This first generation of Graflok backs had winding knobs and no rollers on the bed of the shell. Some people complained that at critical (wide) apertures, these backs weren’t holding the film flat enough for critical focus. In 1958, Graflex consolidated their “Baby Graphic” cameras into a single, less expensive 2×3 camera, the Century Graphic, featuring a molded-in Graflok back (the entire body was made out of a special, very strong plastic called Bakelite). The “23” back was popularized with the Century.
In 1965, Graflex released their 6×9 rangefinder camera, the XL. This camera was designed from the beginning for roll film, and had a 2×3 Graflok back. However, it was unique in that it was not permanently part of the camera, but rather attached through four locking posts. For the first time, the Graflok system became a removable adapter. This allowed other back adapters to be mounted in its place, such as a Polaroid back. Such a back was impossible to mount via the 2×3 Graflok system because it was too large, and thus couldn’t get the film close enough to the camera for it to hit the correct film plane. Now the entire 2×3 back adapter could be removed and replaced with a specially made Polaroid back, or any other back that wouldn’t work via Graflok. This was the most sophisticated and versatile back system ever invented for the medium format world.
When the XL was released, Graflex updated their line of roll film backs to the RH series. They added two new formats to the line: 6×7 120 (RH-10) and 6×7 220 (RH-20), while continuing to make a 6×6 (RH-12) and 6×9 (RH-8). 6X7, which had not been available in the earlier generation of backs, became the most popular size. These new backs were improved in several ways: they used lever winders instead of knob winders, allowing them to be wound faster; they incorporated Graflex’s recent innovation of adding pin rollers within the bed of the shell to hold the film flatter; and they slightly redesigned the film counter so that it could be manually advanced without damage (making it easier to load film). These backs proved to be successful: they had eliminated the two greatest complains about their design. Initially, these were designed with color-coded components (shells, inserts, and darkslides):
Red = 6×9
Blue = 6×7
Aqua = 6×6
Yellow = 220 6×7
These components are all physically interchangeable, and are frequently mixed up in used gear. However, this can cause problems if the format of the insert and shell are mismatched (i.e., overlapping or cropped frames).
In 1968, the Singer Corporation (famous for their sewing machines) bought Graflex Inc. Singer rebranded Graflex’s roll film backs with their own name. Besides this cosmetic change to the line’s shell (adding a flat area for the Singer sticker) and the removal of all color coding, these backs remained mechanically identical.
Graflex went out of business in 1973, selling its camera tooling to Toyo and its roll film back tooling to a company called Subsea (apparently an underwater photography company). For a brief time Subsea continued to manufacture RH series backs under their brand. The example in Mercury Works’ possession is changed from the previous Singer Graflex version in three ways: It contains a silver “Graflex/Subsea” sticker in place of Singer’s; it contains, on the inside of the insert, a silver Subsea sticker with a hand written serial number, and the classic fiberglass darkslide has been replaced with a shiny metal one (apparently darkslides were not included in the Graflex purchase).
During the 1960s, the Japanese company Mamiya released a modular 6×9 camera system aimed at press photographers (thus competing directly with Graflex). The first model of the Mamiya Press utilized Mamiya’s proprietary back system. In 1963, however, in their bid to win over Graflex shooters, they released a version (the “Press G”) with a 2×3 Graflok back. As far as I can tell, however, this appeared not to be a big seller, and they returned to their own “M” back system for the next several models. In 1969, however, they released the final and most advanced model in the series, the Mamiya Universal. This utilized a back system similar to (but incompatible with) the Graflex XL system: the back adapter itself was removable from the camera body, allowing multiple back systems to be used. One such back adapter accepted “M” backs, while another accepted Graflok backs. (A polaroid back was a third option, which eventually lead to a collaboration between Polaroid and Mamiya to release a version designed to shoot Polaroid 600 integral film; this was branded the “Polaroid 600.”) The Mamiya Universal is significant historically because it was perhaps the greatest attempt by a major corporation to produce a modular, open system that would be compatible with components made by other companies (in this case, backs only; not lenses or other components). In this sense it is a precursor to the Mercury. However, it should be noted that its lens system was completely proprietary, so it was only “universal” in the sense that multiple backs from Mamiya, Graflex, and Polaroid could be mounted, including various film sizes. In practice, users still had to rely upon a series of complex adapters made by Mamiya itself if they were to access these options. Today, the Graflok adapters are rare and prohibitively expensive. Ultimately, then, the camera system is not nearly as Universal as it promised. Further, the corporate motivation was not to create an open camera system, but merely to win over some professional users who were heavily invested in Graflex equipment.
In 1970, several years before Graflex went out of business, Mamiya released their 6×7 reflex studio camera system, the RB67. This time Mamiya adopted the 2×3 Graflok protocol as their default back. Like their earlier Press Universal and Graflex’s XL system, the Graflok 23 back was an adapter that could be removed in order to mount other non-Graflok accessories. Mamiya’s innovation, however, was to make the entire Graflok 23 back adapter rotatable, enabling the photographer to switch quickly between landscape and portrait orientations without turning the camera on its side, a time-saving benefit for studio photographers (for whom the camera was designed).
Initially, Mamiya released three different film backs for the RB67: A 6x7mm back in 120 and 220 versions and a unique 645 back. This latter uses 120 film and shoots a 6×4.5cm frame in a vertical orientation. A sticker on the top of the insert and a decorative metal frame on the back remind the user of the format and orientation. Because the RB67 has a rotating back, the orientation of the rectangular frame could be changed to landscape via the camera itself. Mamiya also released a Graflok 23 sheet-film holder. Though regular 6×9 sheet film holders can be modified to work with with a Graflok 23 system (they were originally designed to be held in place by a spring back), Mamiya’s solution, the Double Cut Film Holder, is particularly elegant.
Beginning with the second model of the RB67, the “Pro-S,” in 1975, Mamiya added various interlocks to the back adapter and their backs to prevent common mistakes, such as trying to remove the dark slide when the back was not mounted, trying to take a second exposure before the back was wound to the next frame, etc. These “idiot proof” devices made both the mount and their backs more complex in design. Other changes from the “Pro” to the “Pro-S” line of Graflok backs included different internal rollers (smaller) and a different frame counting mechanism. This system is more accurate and thus allows for slightly better frame spacing consistency, but is not friendly with back modifications to utilize other types of film. Very early on, Mamiya released some transitional Pro-S backs that had the old, larger internal rollers, but the new frame counter and interlocks. The shell looks identical (though it is not), but the insert has a red border around the format sticker (i.e.“220”). Later, Mamiya replaced this transitional design with a non-red-border version.
The Pro-S back lineup added a motorized back and a 70mm back. The motorized back was large, heavy, and required an even more cumbersome NiCad battery back, which was meant to be bolted to the bottom of the already massively heavy camera. It could accept 220 film and was designed purely for studio portraiture. It isn’t very useful today. The 70mm back, however, is a beautiful work of engineering, and the only 70mm back released for the Graflok 23 standard. It accepts industry standard 70mm cartridges, each of which is loaded with up to 15 feet of film. It is slightly larger than the 120 backs in all dimensions. However, you can shoot 50 6×7 exposures on one roll of film with this back! It may be slightly larger than a 120 back, but it is definitely a lot smaller than FIVE of them! This back even contains a vacuum seal pressure plate. This could be utilized optionally through the purchase of an accessory pneumatic bulb. Squeezing the bulb then causes the film to be sucked into the pressure plate to hold it ultra-flat. A button at the base of the bulb is then pressed to release the film once the exposure had been taken. An amazing feature, if definitely in the “overkill” category. Mamiya claimed that it was recommended to counter the natural curl of film that has been sitting in a back for a long time (bent around its rollers). When shooting your first frame after letting the film sit for awhile, this suction system could work its magic. Mamiya engineer’s even designed the 70mm back with a built-in darkslide holder, so users can slide it right into the back of the shell when it isn’t in use. Finally, they added a push-button to the shell release mechanism as an additional safety device. The ordinary latch cannot be slid to the “unlocked” position without holding down the button. Mamiya really went all-out in engineering this back, the most impressive in the Pro-S lineup.
Mamiya’s RB67 Pro and Pro-S backs are beautifully engineered and manufactured. They are extremely precise and reliable, if more bulky in the vertical direction than Horseman’s. However, as Mamiya’s camera was only 6×7, they released no 6×9 backs. Nor did they offer a 6×6 back. (Apparently they manufactured one at the very beginning of the camera, but this back is nearly impossible to find today, if it did indeed exist. I could only find a couple of scattered references to them online, and no images have surfaced. It is possible that some folks are confusing this with Mamiya’s rare 6×6 back for their RZ67 camera.) With these glaring omissions, they did manage to introduce 645 and 70mm to the Graflok 23 standard.
Around the time of Graflex’ demise, another Japanese company, Horseman (a subsidiary of Topcon) decided to adopt the 2×3 Graflok back for their series of 2×3 view cameras. Starting with the 985 around 1975, this was their default back format (their earlier 6×9 cameras had used a similar, but non-standard format). Simultaneously, they released their own series of roll film backs in “8 Exp” 6×9 and “10 Exp” 6×7 formats, each in both 120 and 220 versions. (They also released a matching 6×12 back, but this was for 4×5 cameras only.) These backs are beautifully engineered, high-end pieces of equipment. They’re larger and heavier than the Graflex versions, but include features such as metal darkslides, a film memo holder (which holds the labeled end flap of a 120 box, so you can see at a glance which kind of film was loaded in which back), and an internal exposure counter (which shows through a window in the top of the back). These were manufactured until sometime around the end of the 1990s. I have never seen one that has malfunctioned. The Horseman 8EXP is the best 6×9 back available for the Graflok 23 system.
In 1990, Mamiya released the third major version of the RB system, the RB67 Pro SD. With this camera they updated their line of backs to a more contemporary, “boxy” style. Gone were the chrome highlights and leatherette, to be replaced by acute angles in black plastic. These shells contain better light-leak protection that didn’t rely on foam seals as insurance. In the 6×7 backs (120 and 220), Mamiya incorporated a darkslide sheathing method similar to that which they had implemented with the 70mm back. Finally, after 20 years, Mamiya updated their 645 back to the Pro-SD style. They also produced a new version of their 6×7 motorized back. This one took four AA batteries instead of an external battery back. It is a far superior design. The most impressive Pro-SD back, however, was a new motorized 6×8 back! The Pro-SD camera had the option of exposing a slightly larger, 6×8 frame, and this was the only back that could take advantage of it. The feature had major limitations, the foremost being that it only worked in portrait orientation (when photographers would be less likely to desire a more elongated format). However, the back itself is a marvel, and works perfectly on any other Graflok 23 camera system! (Other cameras will not automatically advance the film after a shot, but this can be accomplished by simply pressing the advance catch or button on the back itself.) This single back is the only 6×8 back ever produced for Graflok 23. It can be advanced with either the built-in motor or by manually advancing its winding knob. Its motorized features are, therefore, completely optional.
Mamiya did not update their 70mm back to the Pro-SD style, but simply continued to manufacture and sell the Pro-S version, just as they had for the Pro 645 back during the Pro-S era.
The Mamiya RB67 system was quietly discontinued shortly after digital back manufacturer Phase One purchased a 45% share in the company in 2009 (Phase One then purchased the company outright in 2015). Since the 1980s, Mamiya’s RZ67 system, which uses interlocked electronic components (shutter, trigger, meter, back), had been competing with the RB67 system. Unfortunately, the RZ system does not use the Graflok standard and thus none of its backs are compatible with Graflok cameras (and vice versa).
Starting in 2015, Mercury Works adopted the Graflok 23 standard for its open camera system, the Mercury. All Graflok 23 backs work with the Mercury. We have also sought to update and expand the Graflok 23 ecosystem by introducing new products to adapt new formats to the Graflok standard. The Mercury 135 Pano modification re-engineers Mamiya RB67 Pro and Pro-S backs to accept 35mm film in a horizontal panoramic orientation (the height of 35mm film and the full width of the 6×7 back). Photographers have long experimented with stringing 35mm film into 120 backs. The lack of a film guide to sandwich the film against the pressure plate, however, has made this a very imprecise method. The Mercury 135 Pano back finally brings professional 35mm film shooting to Graflok 23 cameras. An “extended frame” variant modifies a Mamiya RB67 Pro 645 back for 35mm, shooting a slightly wider than “full frame” image for non-panoramic use. Mercury has also produced a kit to modify RB67 Pro-S backs to shoot 46mm film (also known as 127). This conversion allows the user to load 220 length strips, for twenty 4x7cm exposures.
Mercury has also produced kits to adopt Lomography’s Diana Instant Back (Instax Mini) and Belair Instant Back (Instax Wide) to Graflok 23, allowing photographers to shoot both Fuji Instax formats on any camera that can compensate for their focal plane shift (20mm for the Instax Mini, 30mm for the Instax Wide). The Mercury camera easily compensates for this focal plane shift.
Mercury has also brought digital photography to the Graflok 23 standard with a Mamiya 645 to Graflok 23 adapter. This allows digital backs to mount instantly to Graflok 23 cameras, with a 20mm focal plane shift.
Finally, Mercury will release a simple 120 6×9 roll film back that will utilize the frame numbers still printed on 120 backing paper for frame counting and film advancing. This was the basic method for 120 cameras before the Graflok standard was invented; sadly, no company has carried on this tradition on the Graflok platform until now.
Because three great companies made Graflok standard backs in so many formats for 60 years, there are many wonderful options to choose from! Below we list all known Graflok 23 backs by format.
General Comparison of Capabilities:
It is difficult to compare these brands because each offers products and capabilities that the others don’t. It is impossible to determine which brand is “best.” If you know which formats you wish to shoot, the following section is most useful: it compares options for each format. The following chart, however, summarizes the general features of the various brands. Only roll film backs are included in this table:
|Brand/Series||Years Made||Format Sizes||Film Flatness||Frame Counter||Compactness||Special Features|
|Graflex knob wind||1947-1964||6×6, 6×9||Mediocre||Mediocre||Excellent||Can mount inserts upside down to clear top view.|
|Graflex lever wind||1965-1973||6×6, 6×7, 6×9||Good||Good||Excellent||Can mount inserts upside down to clear top view.|
|Mamiya Pro||1970-1975||645, 6×7||Excellent||Excellent||Good|
|Mamiya Pro-S||1975-1990||6×7, 70mm||Excellent||Excellent||Good||Darkslide interlock|
|Mamiya Pro-SD||1990-~2010||645, 6×7, 6×8||Excellent||Excellent||Mediocre||Full interlocks, motorized options, darkslide holder|
|6×7, 6×9||Excellent||Excellent||Mediocre||Can mount inserts upside down to clear top view.|
135 Full Frame
Mercury has produced a special conversion kit for the Mamiya RB67 Pro 645 medium format back to allow it to accept standard 135 (35mm) film cartridges. Unlike various hacking methods and “adapters” that have existed for years, this fully modifies the film gate for a 24×40mm frame size, eliminating excess light bleed/ internal reflections. Even more importantly, it provides a stabilized path for the film, allowing the pressure plate to hold the edges (perforations) of the film flat. The Mercury 135 Full Frame back will produce a professional image on a flat film plane. The image will be the full, ordinary height of a 135 frame and approximately 40mm wide, for a slightly elongated frame (i.e., slightly larger than Full Frame, for a more cinematic aspect ratio and increased resolution). A typical 35mm 36 exposure cartridge will yield approximately 25 extended-frame exposures in this back. This back is particularly useful to shoot rare films that only exist on 135, or to shoot the Mercury with 135 format lenses (i.e., Canon, Nikon, etc.). Note that the back itself cannot rewind an exposed roll of film back into its cartridge. A changing bag or darkroom will be necessary for that. However, the back kit includes a small crank to make rewinding the cartridge very fast and easy in the dark.
Mercury has produced a special modification of the Mamiya RB67 Pro-S medium format back to allow it to accept standard 135 (35mm) film cartridges. Unlike various hacking methods and “adapters” out there, this fully modifies the film gate for the 24×67 frame size, eliminating excess light bleed/ internal reflections. Even more importantly, it provides a stabilized path for the film, allowing the pressure plate to hold the edges (perforations) of the film flat. Unlike all existing adapters, then, the Mercury 135 Pano back will produce a professional image on a flat film plane. The image will be the full, ordinary height of a 135 frame and approximately 7cm wide. A typical 35mm 36 exposure cartridge will yield approximately 14-15 panoramic exposures in this back. This back is particularly valuable for panoramic aficionados, for the medium format use of uncommon films that only exist in 135 format, and for inexpensive shooting and local developing. Note that the back itself cannot rewind an exposed roll of film back into its cartridge. A changing bag or darkroom will be necessary for that. However, the back kit includes a small crank to make rewinding the cartridge very fast and easy in the dark.
6×4.5 Roll Film
Mamiya RB67 645:
Mamiya made two versions of this back: The early Pro and the late Pro-SD. Both take 16 vertical exposures on a 120 roll of film. This is a very economical way to shoot medium format film; use this with smaller lenses (without the coverage needed for larger formats), when you want to stretch your roll of film as far as it will go, or when you’re shooting longer focal lengths and want as much “reach” as possible. This back shoots in vertical (portrait) orientation, so you will have to rotate the Mercury on its side to shoot landscape orientation. The Pro-SD back can hold the darkslide when not inserted, and adds an interlock to prevent the darkslide from being pulled when the back is not mounted on a camera.
6×6 Roll Film
Knob advance; usually shells are lacking pin rollers. 12 exposures. These backs don’t hold the film quite as flat as the later backs, but this is rarely a problem. Another quirk is that the film counter is linear only: it cannot be manually or automatically reset, so you have to remember to wind it to the end (until it no longer turns) before loading a roll of film! Some backs are labeled “22,” some simply have blank backs. These can be identified as the rare 6×6 variants by the distinctive square front (similar to the RH-12 image below) or by their frame counter, which shows 12 numerals instead of 8. These are uncommon backs.
Lever advance; usually shells have the desirable rollers. Insert is interchangeable with RH-10 shells, but the image must be masked for the 6×6 format or frame overlapping will occur. Because there are so many variants to the RH series, it can be difficult to identify the rare RH-12. Look for the distinctive square frame as shown here, or the frame counter, which counts from 1 to 12. On versions with colored handles, the RH12 is marked by an aqua color (not to be confused with the blue color of the far more common RH-10). These backs are highly valued by square format aficionados. While it is possible to crop a 6×7 frame to 6×6, purists prefer to shoot square from the beginning–plus, you get an extra two frames per roll of film. That and the hipness factor, along with the fact that no other manufacturer released 6×6 Graflok 23 roll film backs, ensures that not only Graflex users, but also Mamiya, Horseman, and Mercury users seek these out.
6×7 Roll Film
Lever advance; shell has desirable rollers. Small and lightweight, these are excellent backs, and the best value. Versions with colored handles are blue. Others, such as the one shown here, have silver or black handles, and sometimes contain the “Singer” plate. Disadvantages: these lack a film clip holder (but usually contain a dry erase patch upon which to write the name of the film), and use synthetic dark slides that can sometimes become cracked. These are common in 4×5 format, so make sure that you purchase the “6×9” or “2×3” or “2.25 x 3.25” format! (The inserts are the same, but the shells are for different format cameras. 3×4 shells exist as well, so it’s easy to end up with the wrong back standard.)
These backs were designed for 220 film. On color coded versions, they are signified by yellow. Other than the color of its handle and its 20 digit film counter, this back looks identical to the RH-10. Like Horseman and Mamiya 220 backs, these will work with 120 film, but will pull it tighter than normal. Some have reported problems with the advance being too tight for comfort, others have reported no problems at all. My advice: don’t be afraid! These can be had at bargain prices. One other issue to note: the leader on 220 film has a slightly different length than for 120, and thus in order to avoid chopping off part of your last frame, you should start the film 1/2” to one inch BEFORE the start marker on the leader if using 120 film. If you do this, the back will operate as normal.
This is the standard back for the RB67 system. Larger in the vertical dimension and heavier than the Graflex backs, these are nonetheless very high quality devices, and are extremely reliable. They utilize high quality metal darkslides. Both 120 and 220 versions work fine with 120 film, though 220 backs do pull a bit tighter, and are bargains, as most folks prefer the 120s at this point. (Also note that when using 120 film in the 220 version of this back, in order to avoid chopping off part of your last frame, you should start the film 1/2” to one inch BEFORE the start marker on the leader. If you do this, the back will operate as normal.) All Mamiya RB67 backs are labeled either “120” or “220” on the top; this is the only way to tell the difference.
All versions of this back work equally well (except the motorized versions, listed below). The Pro-S version added an interlock to prevent the darkslide from being removed when the back is not mounted on a camera. This is a useful feature. The exterior of “Pro” and “Pro-S” versions look identical except for the presence of a small, shiny “Pro-S” insignia on the top right of the rear of the back (as shown above). “Pro” backs lack any insignia whatsoever.
The aesthetics of this back were significantly redesigned in 1990 for the “Pro-SD” version. In this version, the shell contains a slot to hold the dark slide if you want to take it out of the back for rapid shooting. This version also eliminated the internal foam that was meant to be a backup light blocking technique on the Pro and Pro-S version. Instead, the Pro-SD version deepens the light traps in the shell. The Pro-SD version costs significantly more on the used market, but is superior in these minor ways.
Mamiya RB67 Pro-SD 6×7 Motorized:
This is a later version of essentially the same back. It takes four AA batteries. When you press the advance catch, instead of freeing the knob to advance your film, it automatically advances to the next frame. These are not necessary, but work very well, and are pretty cool! They are, however, slightly more difficult to load than their non-motorized counterparts (due to the design of the spool holders), are a bit heavier when they contain the batteries, and lack the dark slide holders of the non-motorized Pro SD backs. They can be operated manually, but only with an advance knob that is a bit slower than the lever. These are fun, but definitely not as practical as the non-motorized versions. Also, beware of an earlier (Pro-S) version of this back. Rather than containing integral batteries, the earlier back required a tethered battery unit that had to be attached under the camera. Avoid these! Only consider a motorized back from the Pro-SD line.
Horseman 10 EXP:
These are less common in Graflok 23 shells (more common in 45), but very high quality backs. Horseman quality and precision. This back is rather large for the 6×7 format (the same size shell as their 6×9 back, which was already large). Because it shares a shell with the 6×9 back, and the only differentiating mark on the back is printed on the memo holder that is usually covered with a film indicator, it is extremely difficult to tell the two sizes apart when they are in your film bag! For this reason, if you are going to use Horseman 6×9 backs, I’d suggest using Mamiya or Graflex 6×7 backs to avoid confusion. This is, however, a top-quality back, and sometimes goes for low prices online as it is less sought-after compared to Horseman’s famous 6×9 variant.
Horseman 20 EXP:
This is the same as the 10 EXP back except that it is designed to accept 220 film. It works perfectly well with 120 film, but note that when using 120, in order to avoid chopping off part of your last frame, you should start the film 1/2” to one inch BEFORE the start marker on the leader. Horseman 120 and 220 inserts are interchangeable, but 220 shells contain one extra threaded post inside to prevent 120 inserts from seating properly. This post can be easily removed.
Mamiya RB67 70mm:
Mamiya released this advanced, beautifully designed back fairly early on, in 1975. Due to its low volume, Mamiya never updated it for the “Pro-SD” line, but continued to manufacturer the original design for most of the system’s life. This back uses standard, reusable 15′ canisters (made by Kodak and a couple of other companies) and shoots in 6×7 format. You will get roughly 50 exposures per cassette! That’s a lot of shooting! Kodak used to sell individual 15′ cassettes in this format, but nowadays you will have to load each cassette yourself from 100′ rolls of 70mm film in a darkroom or changing bag. The RB 70mm back is just like an oversized 120/220 back (it is slightly thicker and slightly taller), except that in order to load it you not only remove the insert from the shell, but also remove the bottom of the insert entirely. Film is spooled out of one cassette and into another, identical, takeup cassette. Unless you tape some leader on your roll, some film will be lost at the head of each roll. No one was concerned with this because in 70mm, you’ve always got film to spare… This back also has a unique feature: a pneumatic socket at the bottom. You can optionally attach an air bulb to this. If the film has been sitting in the magazine for a long time without being used, you’re supposed to give it a pump to ensure proper film flatness. Alternately, you can simply advance an extra frame, which regains tension. Utilizing this vacuum system will hold your film perfectly flat; technically, then, this is the most advanced Graflok back available with regard to film flatness.
One significant downside to this excellent back is that it officially requires Type II perforated film. Some old 70mm film contains Type I perforations, and a lot of 70mm film is unperforated, including almost all Kodak Portra. The back doesn’t use sprockets to advance the film, but merely to count how much film has been advanced, so that it knows when to stop the lever advance and increment the frame counter. You have three options with this back: Shoot perforated film only (make sure that any film you buy explicitly specifies “Type II perf”), or modify the back by grinding or filing off the sprockets and using oral rubber bands in their place. Unperforated and perforated film alike will be able to turn the frame counter after after this modification.
6×8 Roll Film
Mamiya RB67 6×8:
This is a late model back, designed for the RB67 Pro-SD camera in the 1990s. It only comes in a motorized version. Expensive, but unique: this is the only 6×8 back ever made for the Graflok system. It gets 11 exposures on a roll of 120 film (22 on a roll of 220), and some consider it the ideal compromise between the film thriftiness of 6×7 and the wide landscape format of 6×9. The back can be switched from 120 to 220 mode. It takes four AA batteries. With those installed, it will automatically advance to the next frame of film after every shot taken on an RB67 Pro-SD camera. On other cameras, you can press a button on the top or flick the “advance lock” lever on the back to trigger the back to advance to the next frame. Alternately, you can use the back’s knob to advance manually, if your batteries are dead or you simply prefer manual operation. This back could only expose the full 6×8 frame on the later Mamiya RB 67 Pro-SD model camera, and only in the portrait orientation! However, you can now harness its full potential in landscape orientation on the Mercury.
6×9 Roll Film
This is the original Graflok 23 back for which the standard was invented! Knob wind, usually lacking the desirable pin rollers in the shell (those came about a decade after this back’s debut). As a result, these may not hold your film quite as flat as the later backs, which could affect focus, but only at very wide apertures and close distances. Another quirk is that the film counter is linear only: it cannot be manually or automatically reset, so you have to remember to wind it to the end (until it no longer turns) before loading a roll of film! These are the only relatively plentiful 6×9 backs out there, and represent a good bargain to get into the format.
These are later backs that are lever wind, and usually contain the pin rollers to hold the film flatter. These are high quality backs. They are definitely less common than the “23 Graphic” 6×9 backs as well as all of the Graflex 6×7 backs. Disadvantages: these lack a film memo holder (but usually contain a dry erase patch upon which to write the name of the film), and use synthetic dark slides that can sometimes become cracked. These are common in 4×5 format, so make sure that you purchase the “6×9” or “2×3” or “2.25 x 3.25” format version! (The inserts are the same, but the shells are for different format cameras; 3×4 versions exist as well, so beware.) These are highly recommended, but generally command a premium price.
Horseman 8 EXP:
This is a very high-end back. Horseman quality and precision, along with the generous dimensions of the 6×9 format, have made this a famous back, in both Graflok 23 and Graflok 45 variants. Like Graflex roll film backs, the online shopper must be very careful to ascertain which Graflok standard a particular Horseman back is for. The mechanics are the same, and even the shell looks the same except for a larger front plate in the 4×5 version. This larger plate should be visible from most angles; the Graflok 23 version has a mating plate that is slightly smaller than the footprint of the back as a whole; the inverse is true for the Graflok 45 version. (Unlike Graflex backs, there is no 3×4 version to add further confusion.) This back is less common than the Graflex 6×9 models, and commands a higher price. Most are located in Japan. This is the highest quality 6×9 back available for the Graflok standard.
2.25 x 3.25 sheet film
2×3 Sheet Film Holder:
A number of brands make sheet film holders in this format. Each holder holds two sheets, one on each side. Older wood and newer plastic versions exist. You need to load these yourself in a darkroom. They function just like miniature versions of 4×5 holders. Technically, these standard holders are not Graflok 23 backs, as they lack grooves for the Graflok sliders to lock into. They do, however, seat perfectly in Graflok 23 cameras, including their light blocking ridge, provided that some mechanism can hold them in place. Before the Graflok standard even existed, these holders would work with “spring backs” that could be pulled open far enough to insert the holder; springs would then press the holder against the camera. Graflex and Horseman cameras that use the Graflok 23 standard also contain removable spring backs, so both systems can be employed. The Mamiya RB67 and Mercury are designed with Graflok-only backs, so an alternate means of attaching film holders must be devised. Rubber bands or tape can be used in a pinch. In addition, it is possible to carefully mill grooves into wood holders so that these holders can be firmly attached to a Graflok back.
Graflex also manufactured a 2.25 x 3.25 cut film holder for their early SLR line of cameras (labeled “Graphex” instead of “Graphic”). These holders actually contain grooves that allow them to be mounted on a 2×3 Graflok back such as the Mercury’s. This is handy, and these holders are also a bit shorter on the non-image-area section, which makes them more compact. On the downside, they lack the Graflok ridge on the right side that locks into the Graflok back adapter’s groove for correct placement and extra light sealing. Instead, they contain a groove (the Graphex system was inverted). You can glue on a ridge yourself if you wish; Mercury Works makes a simple one. Otherwise, you can just be sure that the holder is carefully pressed against the left edge when you lock it in place. At any rate, these holders are quite rare.
Mamiya, too, released an uncommon “Double Cut Film Holder,” which was not only Graflok mountable (for the RB67), but was adaptable from sheet film to plate film. This one is highly recommended! Just be aware that there are two “types”: Type A and Type J. They hold different sized film. The Type J holds 2 ¼ x 3 ½ (6.5 x 8.9cm) sheets, rather than 2 ¼ x 3 ¼ (the Type A). The only Type J sheet film still manufactured is Fomapan 100 (the same as Arista 100), and you have to purchase it straight from Foma in the Czech Republic, here. However, rumor has it that the Type J holders can still hold Type A film. Also be aware that Mamiya also produced a cut film holder for the Mamiya Press camera. This will not work on Graflok 23 cameras! Online auctions often won’t differentiate, so you have to do so visually. The Press holders only hold one sheet, and the two sides are different: one side with a dark slide to hold the film, and another flat side with leatherette. The proper holders are double sided, and hold two sheets. Both styles come in Type A and Type J versions.
Only four film stocks are still available in sheet film format: Ilford FP4+, Ilford HP5+, Arista 100, and Arista 400. All are available from Freestyle Photographic Supplies, at decent prices. The Arista is quite cheap. The 400 speeds are the most useful, and in my opinion, worth the effort of sheet film. Sheet film allows you to rate each shot at whatever ASA/ISO you want, and then process it to that spec later. This is particularly useful for high latitude, high-ASA films (like HP5+, which is a fabulous film stock), which give you quite a range of options. This isn’t available for roll films, as you have to shoot the entire roll at the same ASA. Other rare films can be cut down from 4×5 to 2.25 x 3.25 size. Of particular note is Arista’s Ortho Litho 3.0 film, which can be cut in a darkroom with a red safelight, and produces results unlike anything available in 120 format!
This unique device, manufactured by Graflex, uses the same 2.25 x 3.25 sheet film as above, but holds six sheets instead of two! An ingenious mechanism allows each sheet to be exposed in succession, with a handy film counter letting you know where you are and when you’re done. It’s as fast and easy to use as a roll film back (but definitely more difficult to load). Grafmatics have several advantages over standard sheet film holders:
They are much faster to operate, as you don’t have to flip over or replace a film holder for every successive shot. This was a big deal back in the press days. Only pack film was faster.
They make it easier to keep track of your exposures. No need to figure out which holders have been exposed, which have been unloaded, etc. Here, you shoot until all six sheets are exposed, then unload it all at once.
It is more compact than multiple film holders. It’s just a bit bulkier than a single film holder, but it holds three times as many shots!
It doesn’t require a spring-loaded focus panel. The Grafmatic is clamped onto the camera via the the Graflok system. Thus it works without modification with the Mercury camera. (Note that the Grafmatic could also be used with a spring back on old Graflex cameras, without the need of a Graflok back. This makes it extremely versatile.)
The only downside to the Grafmatic over a sheet film holder is that you can’t shoot just one or two sheets and develop them right away. You could open up the Grafmatic in the dark and “rob” it of an exposed shot to develop, but this is not recommended, as you would have to find the exact sheet you want and leave the others in the proper order. Then the frame counter would no longer accurately tell you when all of your sheets are exposed, either. The other downside is that these are more difficult to load than sheet film holders, which are a real cinch.
These were made in 2×3 and 4×5 format sizes. The correct sized Grafmatic is labeled “23” on the front (though some later models, like the one pictured here, have red lettering on the front, and only mention the exact size on the underside, in stamped black letters that are difficult to read). Grafmatics come in 23 and 45 sizes, and unless you see the label or can determine the scale, they look identical. These are far more rare than roll film backs, and are quite popular among large format shooters, but the 23 version can often be found inexpensively.
These are highly recommended for the Mercury camera, provided that you take the time to learn and practice the loading technique to avoid bending the delicate septums (the little slides that hold the film). Because few people shoot 2×3 sheet film anymore, these can often be had at half the price of the still popular 4×5 versions, and less than a typical roll film back.
Online instructions: https://www.graflex.org/speed-graphic/grafmatic/
Fuji Instax Film
Mercury Instax Mini Back:
Mercury has developed a kit to modify a Diana Instant Back to the Graflok 23 standard. The back has a frame counter and electronic ejection/development of the film. The Mercury kit includes parts that replace a number of the original ones, building up a Graflok 23 armature. This back sits 20mm farther back from the film plane than a standard Graflok 23 back. Due to the design of the Diana Instant Back, it interferes with most Graflok mechanisms. It can only be properly mounted on a Mercury camera. Mercury Works has developed both a darkslide version and a non-darkslide version of this conversion kit.
Mercury Instax Wide for 23:
Mercury has developed a kit to convert the Belair Instant Back, which takes Instax Wide film, to the Graflok 23 standard. This back sits 30mm farther back from the film plane, and thus requires the removal of 30mm of front spacers. Mercury has developed both a darkslide version and a non-darkslide version. We have also developed a special ground glass back that matches this film plane and provides the larger area to match this format’s size (which is larger than 6×9).
Polaroid 100 Film
Horseman Polaroid Back:
Horseman is the only company that produced a Graflok 23 back for Polaroid 100 film (The Graflex XL and Mamiya RB67 had Polaroid 100 backs, but they both bypassed the Graflok system and mounted using alternate methods). This back sits 10mm farther back than the usual film plane, and must be compensated for my removing front spacers. This back is not able to expose the entire area of the film, but only a 6×9 section of it. This didn’t matter for exposure testing, but makes this back less useful today: the resulting images aren’t really presentable, and the now-discontinued film (in 2016 by Fuji) has become quite expensive, so this isn’t a popular way to shoot it. However, this could still be used to produce 6×9 emulsion lifts or emulsion transfers, both of which are possible with (expired) Fuji FP-100C film.
No digital back manufacturer has released a medium format digital back that utilizes the Graflok 23 mount. There are economic reasons for this, but also technical: the Graflok 23 mount insets the back inside the back adapter and locks it in place from above. This makes it a difficult mount for large or awkwardly shaped backs. The solution is to shift the film plane back to provide extra room to clear the Graflok locking mechanism, as was done in the cases of the Horseman Polaroid Back and the Mercury Instax backs. The Mamiya RB67, however, the greatest candidate for digital back usage, is unable to shift its film plane (because it is a reflex camera), so when Mamiya made a digital back adapter, they bypassed the Graflok system and utilized the camera’s more primitive mounting system (which requires the complete removal of the Graflok back adapter). They also charged $1500 for it, which pretty severely limited digital back adoption on that system.
Mercury Works, however, has created a Mamiya 645 to Graflok 23 adapter that allows digital backs to be adapted to the Graflok 23 standard. This adapter is compatible with any Graflok 23 camera, but because it shifts the film plane by 20mm, it isn’t practical to use on a Mamiya RB67.
Horseman Angle Viewfinder
This viewer is actually two-in-one: it is a ground glass back with a detachable hood. The hood features a right-angle monocular magnifier for viewing in full daylight without a dark cloth or loupe. Remarkably, the eyepiece swivels, allowing you to view the ground glass from any angle. In the standard orientation, a mirror in the eyepiece reverses the ground glass image so that it is displayed with proper left-right handedness (though the image is still rendered upside down). This is a pricey and somewhat bulky item, but very impressive and potentially useful for some.
Horseman Rotary Back
Another remarkable feat of engineering from Horseman, this is perhaps the most mechanically complex Graflok 23 accessory. It basically splits your single Graflok 23 back adapter (on your camera) into two such receptacles, vertically stacked. At any given time, one is “live” (in the camera’s light path) and the other is upside down, above, with a light blocking mechanism in place (obviating the need to close a darkslide in the upper back). To switch between the two backs, you only need to rotate the apparatus. This brings the upper back into the light path, opens its light-blocking mask, and closes the mask on the other back. The obvious, and intended, use for this device is to attach both a film back and ground glass back at the same time, switching instantly between them rather than being forced to remove one to mount the other. Other configurations are possible, however: two different film backs, for instance. It works quite well, but at the expense of a lot of added bulk and weight! This is a tripod-only solution, and probably best reserved for studio/indoor use.
PDF manual available here.
Horseman Optical Exposure Computer:
Yet another impressive Graflok 23 innovation by Horseman, this is a through-the-lens (TTL) exposure meter. It has grooves that allow it to mount like any other Graflok 23 back, though a large section of the back protrudes from the right side of the camera. A turn of the large knob on the right side turns on the meter and allows you to select between three different ranges of possible values. Here you set your f-stop, open your shutter, and take a reading. The meter’s needle will point toward the proper shutter speed, as calculated by averaging the exposure across the entire 6×9 frame. The large round dial sets your ASA. A transparent dial in front of that allows you to position a reference marker if you wish. The device is faster and easier to use than most light meters, and of course has the advantage of metering your actual frame. It thus takes into account the actual (not merely nominal) speed of your lens at a given f-stop, any filters in the light path, and any extra extension (“bellows factor”) on the lens. These features, however, come at the expense of bulk (the device is rather large) and time (you have to mount this on the camera rather than just taking a reading as you would with an incident meter).
The original version of this meter required two different batteries. The “A” battery is a PX-26, and covers the low range of values. The “B” battery is a PX-640, and is necessary if you wish to meter in very bright conditions. Both batteries were originally Mercury (the toxic metal, not the camera system) types. The same problems exist as with any older light meters that use Mercury batteries: replacing them with alkalines yields a changing voltage, which will result in altered meter readings over the life of the battery; using Silver Oxide batteries will produce a constant voltage, but it will still be incorrect because of mismatched voltage. Moreover, it is very difficult to find modern batteries in the PX-26 form factor. Even the PX-640 is a rather rare form factor (but it is available, at least in alkaline chemistry). Your best bet is to physically adapt four SR44 batteries (which are silver oxide) for the A battery. Mercury Works makes an adapter that does this. This solution will yield a voltage that is slightly too high (6V instead of 5.6V), but this has little effect on the meter, as low light settings are less affected by voltage differences than bright light settings, and this device is only using this battery for the low light range. The other two ranges are powered by the B battery. For this, you can either adapt a single Wein MRB675 Zinc-Air battery to fit the compartment (which will give you perfect voltage but only several months of life per cell), drain a semi-common A640PX alkaline battery (the intended replacement for the old mercury version) to 1.35V and use it sparingly, or purchase this awesome (but expensive) adapter set, which will allow you to use cheap and common 392 silver oxide battery and will convert the voltage to meter properly. Horseman also released a later version of this meter, all black instead of silver, which uses four SR44 batteries and internal voltage regulators/reducers to eliminate the issue. That model, however, is far more rare and expensive.
Overall, this meter is impractical for most, as a small incident meter will be far easier to maintain, cheaper to purchase, lighter and smaller in your kit, and faster to use. However, those who stack multiple filters or shoot macro, or just want to show off cool gadgets, may find this useful.
Mercury 6×9 Ground Glass Back
Other than Horseman’s elaborate Angle Viewer, this is the only ground glass back ever released for the Graflok 23 standard. Most cameras that utilize Graflok 23 either contain ground glass spring backs (Graflex, Horseman) or incorporated reflex focus systems (Mamiya RB67). The Mercury ground glass back can be used on any Graflok 23 camera. A special variant also exists that extends the film plane back 20mm, to match the Mercury Instax Mini converted back and the M645 to Graflok 23 Digital Back Adapter. Another variant expands the glass to the size of Instax Wide film, matching the film plane of the Mercury Instax Wide for Graflok 23 converted back. Mercury ground glass backs are compatible with all Graflok 23 cameras.
Mercury Rear Spacer
This is a Graflok 23 extension. It mounts to the back of a Graflok 23 camera, then provides a second (simplified) Graflok 23 mount for any back, allowing that back to shift its film plane. It exists in 20mm and 30mm versions and is compatible with all Graflok 23 cameras.
Appendix 1: Camera Compatibility
Because Graflok 23 is a standard, you might expect all Graflok 23 backs to work on all Graflok 23 cameras. This is not the case, due to different designs and manufacturer-specific “extensions” to the standard. I have not extensively tested all combos, but here are some general notes about compatibility:
Graflex’s line of Graflok 23 cameras (Baby Graphics, Century Graphic, and Graflex XL) can accept backs by all three manufacturers, but care must be taken that their spring back clips (which hold the ground glass spring backs when not using Graflok accessories) don’t interfere with the backs. In practice, these sometimes need to be bent very slightly, or they will subtly prevent other brands’ backs from seating flush to the camera back—and thus the film plane. In addition, the darkslides on Mamiya RB67 backs (all styles) cannot fully close when mounted on a Graflex camera without modification (cutting off one side of the metal hooks that protrude from the darkslide handle). Of course, Mamiya backs cannot achieve the full 6×9 aperture that the Graflex cameras are capable of.
The Mamiya RB67 will not accept Horseman backs. Their interlock system makes contact with the Horsman shell, preventing it from being mounted. Graflex backs seem to work fine on the RB67.
Horseman’s Graflok 23 cameras (the 985, VH, and VH-R) can accept Graflex and RB67 backs.
The Mercury Graflok 23 back adapter is compatible with all three major brands of backs.
Appendix 2: Nominal sizes vs. actual measurements of frame
56 x 40
56 x 56
56 x 66.6
56 x 67.7
57.6 x 67.7
Graflex sheet film
52 x 78
Other sheet film
54 x 78 (varies by manufacturer)
56 x 74.5
56 x 81.5
57.6 x 83.5
56 x 112
Appendix 3: Film Plane Measurements
The Graflok standard is about 4.75mm from the base of the Graflok plate to the film plane. In practice, however, every back is designed a bit differently. Film and backing paper are each about 0.1mm thick, so measuring from the Graflok plate to the pressure plate should yield about 4.95mm distance. Sheet film comes in different thicknesses, roll film sometimes includes backing paper and sometimes doesn’t (120 vs. 220). Cartridge film (35mm and 70mm) never has backing paper (but the film itself comes in different thicknesses). The best way to compare backs is to measure directly to the pressure plate (even though this is still an imperfect comparison). Here are some results that I obtained, demonstrating how much variance there is in this standard:
Graflex RH10: 5.15
Horseman 8EXP: 4.7
Mamiya RB67 Pro: 4.85