What exactly does the lever/switch at the top of the Mamiya RB67 120 filmback do?

I'm taking a studio photo course, and we have to use those. 2 instructors have told me that this switch has to be pushed between shots (before the film advance) or else the frames won't space properly. Is that correct?

A related question: I got to frame 9 last night, and the shutter was cocked but wouldn't fire, and I tried everything. So I took the filmback off and discovered I had to flip that switch to get the film to advance. Any suggestions why the shutter wouldn't fire? Thanks in advance for yo

-- Dave Anderson (DavidA@hsonline.net), November 22, 1999

Answers

Dave,

The sliding switch located at the top center of the back allows you to advance to the next frame without making an exposure. For example, you might want to unload your film but you have only exposed 8 frames. It will also let you advance the film when the back is not on the camera.

The small lever adjacent/under the film advance lever allows you to double expose a single frame. When positioned so that the red dot shows you can re-cock the shutter and make another exposure on the same frame.

The camera will not make an exposure unless the filmback is properly positioned vertically or horizontally. Check to see that it is seated in position well. There is also a shutter safety located at the release button that may be slightly turned. Either of these may have caused your "not firing" problem.

Rick

-- Rick Stiles (rick.stiles@lmco.com), November 22, 1999.

Hi David,

The purpose of the lever/switch you are referring to depends on which version of the RB you are using. The RB67 and RB67 Pro use this lever to release the film back once an exposure has been made. In the manual it is referred to as the wind-stop release lever. The winding process is done in three steps in these versions. 1)Press the release lever, 2) wind the film back, and 3) cock the shutter. The RB67 Pro S bodies/backs automated the release of the wind-stop in the film back and only require a two step winding process (it eliminates step 1). The Pro S backs kept this feature for the purpose Rick stated above, as well as allowing its use on the older RB67 and RB67 Pro bodies. The Pro S bodies can also use the older non-Pro S backs, but you will have to use the three step winding process above.

The double exposure lever Rick mentioned is a feature only on the later Pro S backs and it was added for double-exposure prevention. If you are using an older back, it won't have this feature, as you can just cock the shutter and shoot a double exposure.

Lastly, to add to the above comments on your inability to shoot your last frame, if you had inserted the dark slide between exposures and didn't remove it, that would keep you from firing the shutter as well. These are just a couple of things that may prevent you from shooting aside from a back that may need servicing.

I hope this helps you out. If you want, you can email me directly and I can try and help you out with any specific questions you have. I own both RB Pro and RB Pro S bodies and backs, so I could probably give you some insight into their operation.

Good luck!

James

-- James Wolfe (jameswolfe@jps.net), November 23, 1999.