The Polaroid CB-70 film back is used to adapt Polaroid cameras and large format cameras to utilize standard 70mm roll film, expanding their creative possibilities beyond instant photography. This allows photographers to capture a significantly larger number of images per loading, use a wider variety of film stocks, and often achieve better image quality than traditional Polaroid instant film.
What is the Polaroid CB-70 and Why is it Important?
The Polaroid CB-70 represents a fascinating bridge between the instant gratification of Polaroid photography and the versatility of traditional film formats. While Polaroid cameras are renowned for their self-developing prints, the limitations of instant film – cost, availability, and the unique aesthetic – often restricted their use. The CB-70 film back addresses these limitations, providing a pathway for photographers to leverage the strengths of their Polaroid cameras while embracing a broader range of photographic techniques.
By replacing the standard instant film back with the CB-70, photographers can load 70mm roll film, commonly used in medium format cameras. This immediately unlocks several advantages:
- Increased Capacity: Instead of being limited to 8-10 instant exposures, photographers can now shoot 70-100 frames per roll, depending on the camera and framing.
- Film Stock Variety: The CB-70 allows the use of a vastly wider array of film stocks, including black and white, color negative, and color slide film, each with its own distinct characteristics and aesthetic qualities.
- Cost-Effectiveness: Roll film, especially in bulk, is often significantly cheaper per frame than Polaroid instant film.
- Improved Image Quality: While Polaroid film has its charm, roll film often offers superior resolution, tonal range, and overall image quality, particularly when processed professionally.
The CB-70 is particularly valuable for photographers who appreciate the mechanics and ergonomics of Polaroid cameras but desire the control and flexibility of traditional film photography. It’s a tool for repurposing classic cameras and extending their lifespan in a world dominated by digital imaging.
Understanding How the CB-70 Works
The CB-70 film back is a mechanical device designed to hold and advance 70mm film. Its operation is relatively straightforward, although a clear understanding of its features is crucial for successful use.
Key Components and Functionality
The CB-70 typically includes the following components:
- Film Spool Holders: These hold the supply and take-up spools of 70mm film.
- Film Transport Mechanism: This system advances the film after each exposure, ensuring proper spacing between frames. This can be a manual crank or a motorized system depending on the specific model and the camera it’s adapted to.
- Dark Slide: This protects the film from light when the back is removed or the film is being loaded.
- Frame Counter: This indicates the number of exposures taken.
- Pressure Plate: This ensures that the film is held flat against the focal plane for sharp images.
- Camera Interface: This is the mechanism by which the film back attaches to the camera body. This is usually a Graflok back for large format cameras or a custom adapter for Polaroid cameras.
Attaching and Using the CB-70
Attaching the CB-70 usually involves removing the standard Polaroid film back and replacing it with the CB-70. This process varies depending on the camera model and the adapter used. Once attached, the film is loaded into the back in complete darkness (or a changing bag). The dark slide is then removed, and the camera is ready for shooting. After each exposure, the film is advanced using the film transport mechanism. After the last exposure, the film is wound onto the take-up spool, and the dark slide is re-inserted before removing the back from the camera for development.
Frequently Asked Questions (FAQs) About the Polaroid CB-70
Here are some commonly asked questions regarding the Polaroid CB-70 film back:
1. What Cameras are Compatible with the CB-70?
The CB-70 is most commonly adapted to Polaroid 110A/B and 120 Land cameras, as well as large format cameras with Graflok backs. Adaptations are sometimes possible for other cameras with significant modifications.
2. Do I Need Any Special Tools or Adapters to Use a CB-70?
Yes, you typically need a specific adapter plate to mount the CB-70 onto your Polaroid camera. These adapters are often custom-made or difficult to find, requiring research and potentially specialized machining.
3. What Type of 70mm Film Can I Use?
You can use any 70mm roll film compatible with medium format cameras, including 120 film (which is wider than the 70mm width used by the CB70 and needs to be slit before loading) and 220 film. Black and white, color negative, and slide film are all viable options. Careful attention needs to be paid to how the film is slit to avoid light leaks.
4. Is it Difficult to Load Film into the CB-70?
Loading 70mm film into the CB-70 requires practice and patience. It must be done in complete darkness (or a changing bag) to prevent light leaks.
5. How Do I Determine the Correct Exposure Settings When Using the CB-70?
Exposure settings depend on the film stock you are using and the lighting conditions. Using a light meter is highly recommended. Start with the film’s ISO rating and adjust aperture and shutter speed accordingly.
6. Where Can I Find a CB-70 Film Back?
CB-70 film backs are rare and often found on the used market, such as eBay or specialized camera forums. Be prepared to pay a premium for a functional unit.
7. How Much Does a CB-70 Film Back Typically Cost?
Prices vary widely depending on condition, availability, and included accessories, but expect to pay several hundred dollars or more for a working CB-70.
8. Can I Use the CB-70 With a Digital Back Adapter?
While theoretically possible, adapting a digital back to a CB-70 is highly uncommon and technically challenging. Digital backs are typically designed for specific camera systems.
9. What Are the Common Problems Associated With the CB-70?
Common issues include light leaks, film jamming, and mechanical malfunctions due to age and wear. Proper maintenance and careful loading are crucial.
10. Is There a Modern Alternative to the CB-70?
Modern alternatives are limited, as the CB-70 catered to a specific niche. Some photographers explore adapting other film backs, but this often requires significant customization. The most common modern equivalent is using a medium format camera directly.
11. Does Using the CB-70 Change the Image Format or Crop Factor?
Yes, the CB-70 effectively transforms your Polaroid camera into a medium format camera. The resulting image format depends on the specific CB-70 model and the aperture mask used. You can expect a rectangular medium format image, although precise dimensions will vary.
12. What kind of maintenance is involved with the CB-70?
Regular cleaning of the film path and pressure plate is essential to prevent scratches and artifacts on your film. Lubricating moving parts with a specialized lubricant designed for camera mechanisms can also help ensure smooth operation. Consult a camera repair professional for more complex maintenance needs.
Conclusion
The Polaroid CB-70 film back offers a unique and rewarding pathway for photographers seeking to combine the allure of classic Polaroid cameras with the versatility of traditional film photography. While acquiring and using a CB-70 can present certain challenges, the creative possibilities and the ability to breathe new life into vintage equipment make it a worthwhile endeavor for dedicated film enthusiasts. Its a testament to the enduring appeal of analog photography and the power of adaptation in a constantly evolving world of image capture.