The short answer is no. A Mamiya 6×9 film back designed for the Mamiya 7 or similar rangefinder cameras will not directly fit onto an RB67, a medium format SLR. The physical dimensions, mounting mechanisms, and lens registration distances are fundamentally different between these two camera systems.
Understanding the Core Differences: Mamiya 6×9 vs. RB67
The question of interchanging film backs between the Mamiya 6×9 and the RB67 is a common one, often driven by a desire to utilize the readily available 6×9 format on the robust RB67 system. However, several crucial factors preclude this possibility.
Camera Architecture
The Mamiya 7 (and other Mamiya 6×9 rangefinders) are fundamentally different in design compared to the RB67. The Mamiya 7 is a rangefinder camera, characterized by its compact size, fixed lens (or interchangeable lenses requiring no mirror box), and rangefinder focusing system.
The RB67, on the other hand, is a single-lens reflex (SLR) camera. This means that it utilizes a mirror system to allow the photographer to view the scene directly through the lens. This design necessitates a larger body and a longer flange focal distance (the distance from the lens mount to the film plane) to accommodate the mirror’s movement.
Back Mounting Systems
The Mamiya 6×9 backs typically employ a simple clip or lever mechanism for attaching to the camera body. This mechanism is designed for the specific dimensions and mounting points of the Mamiya 7 series.
The RB67 utilizes a rotating back design secured by a more robust locking mechanism. This system is essential for allowing the camera to be rotated for portrait or landscape orientation without having to detach the back completely. The RB67 back also integrates seamlessly with the camera’s light-tight seals and focusing system.
Flange Focal Distance and Lens Compatibility
A significant barrier is the flange focal distance. The RB67’s longer flange focal distance is necessary to accommodate the mirror box. Using a Mamiya 6×9 back on the RB67 would require substantial modification to the lens system and would likely result in incorrect focusing and light leaks. Moreover, the Mamiya 7 lenses themselves are not designed to cover the image circle required by the RB67’s larger film format.
Addressing the Desire for 6×9 on the RB67
While a direct swap isn’t possible, there are alternative paths to achieve the desired 6×9 format using the RB67, albeit not in the traditional sense.
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Cropping: The RB67’s native 6×7 format is very close to 6×9. Simply cropping the image in post-processing (or when printing from the negative) to a 6×9 aspect ratio can achieve the desired result. This is the simplest and most cost-effective solution.
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Modifying RB67 Backs (Potentially): While highly complex and generally discouraged, some advanced camera technicians may attempt to modify an existing RB67 back to mask the film area down to 6×9. This would require meticulous work, potentially compromising the integrity of the back and introducing light leaks. It’s a risky and expensive endeavor.
Frequently Asked Questions (FAQs)
H2 FAQs About Mamiya 6×9 and RB67 Compatibility
H3 1. Why is the flange focal distance important?
The flange focal distance is critical because it determines the correct distance between the lens and the film plane for proper focusing. If the flange focal distance is incorrect, the lens will not be able to focus sharply on the film. Each camera system has a specific flange focal distance that is crucial for lens compatibility.
H3 2. Are there any adapters that can make a Mamiya 6×9 back fit the RB67?
No, there are no commercially available adapters that can reliably and safely adapt a Mamiya 6×9 film back to an RB67. The differences in mounting systems, flange focal distance, and light sealing requirements make such an adapter impractical. Creating a functional adapter would require extensive modification and is generally not feasible.
H3 3. Could a custom adapter be made?
While technically possible, creating a custom adapter is extremely complex and expensive. It would require precision machining, extensive knowledge of both camera systems, and a significant understanding of optics and mechanics. The resulting adapter would likely be bulky, unreliable, and prone to light leaks. The cost of such an adapter would likely outweigh the benefits.
H3 4. Is it possible to use Mamiya 7 lenses on the RB67?
No, it is not possible to use Mamiya 7 lenses on the RB67. The lenses are designed for different camera systems with distinct lens mounts and flange focal distances. Attempting to mount a Mamiya 7 lens on an RB67, even with an adapter, would likely result in damage to both the lens and the camera.
H3 5. What are the advantages of the 6×9 format over 6×7?
The 6×9 format offers a slightly wider aspect ratio and a larger negative area compared to 6×7. This can result in greater detail and less grain when making enlargements. Some photographers also prefer the aesthetic proportions of the 6×9 format.
H3 6. What are the benefits of using the RB67 over a Mamiya 6×9 camera?
The RB67 is a versatile and robust system with a wide range of available lenses and accessories. It offers precise focusing, excellent build quality, and the ability to rotate the back for portrait or landscape orientation. The RB67 is also known for its bright viewfinder and reliable operation.
H3 7. Does the RB67 have any backs that offer different aspect ratios?
The RB67 system primarily uses 6×7 format backs. However, some specialized backs were produced (though rare) that allowed for different frame sizes. These are typically for specific purposes, like Polaroid instant film or roll film formats other than 6×7. No native RB67 back mimics a true 6×9.
H3 8. Are there any other 6×9 cameras that are similar to the RB67?
There are other medium format cameras that shoot 6×9, but none that share the exact feature set and SLR design of the RB67. The Graflex XL series, for instance, is a rangefinder camera that uses interchangeable backs and lenses and offers 6×9 as an option.
H3 9. If I want the 6×9 look, is cropping the 6×7 frame the best option?
For most photographers, cropping the 6×7 frame is the most practical and cost-effective solution. The difference in image quality between a native 6×9 and a cropped 6×7 is often negligible, especially for smaller prints.
H3 10. How can I ensure the best possible image quality when cropping 6×7 to 6×9?
To maximize image quality when cropping, use the sharpest possible lenses for your RB67 and ensure accurate focusing. Shoot at optimal apertures (typically between f/8 and f/11) and use a tripod to minimize camera shake. Scanning or printing the full 6×7 negative at high resolution will also provide the most detail to work with during cropping.
H3 11. Is there any impact on the number of exposures per roll of film when shooting 6×7 with the RB67 compared to 6×9?
A standard 120 roll of film will yield approximately 10 exposures in the 6×7 format using an RB67 back. A true 6×9 camera, or modified 6×9 back, would typically yield fewer exposures, around 8.
H3 12. What are the potential downsides to attempting to modify an RB67 back for 6×9?
Modifying an RB67 back is fraught with potential problems. These include light leaks, unreliable film advance, damage to the back mechanism, and a loss of resale value. The modifications may also not be reversible, permanently altering the functionality of the back. This option should only be considered by highly experienced camera technicians with the proper tools and expertise. It’s generally not worth the risk or expense.