RB67 "T" Exposure Question.

[Donald Qualls]

Then someone has to tell Mamiya that they do not know how to follow industry standards.

Can't do it -- my time machine is broken. Near as I can tell, the 1970s are permanently inaccessible.

 

[ChristopherCoy]

Can't do it -- my time machine is broken. Near as I can tell, the 1970s are permanently inaccessible.

Well that's just unacceptable. I want to speak to your manager.

 

[choiliefan]

Do RB67 lenses have a B setting?

 

[ChristopherCoy]

Do RB67 lenses have a B setting?

no.

 

[Alan Edward Klein]

I would place the real blame on Seiko, the shutter manufactrer. Even on the later electronically controlled Seiko lens shutters, T was terminated by sliding the T control, not by depressing the shutter button again...and similar operation was on Bronica's Seiko electronic shutter.

Well, Mamiya is ultimately responsible. It's their camera. Seiko is just a subcontractor who works for Mamiya. They should have gotten Seiko to change their design or get another supplier. It was Mamiya's choice not too.

 

[Donald Qualls]

For a camera designed primarily as a studio tool, I don't know that the slightly awkward method of making long exposures is that big a deal -- and it's certainly not difficult to actually do, once you know what needs to be done.

 

[MattKing]

Well, Mamiya is ultimately responsible. It's their camera. Seiko is just a subcontractor who works for Mamiya. They should have gotten Seiko to change their design or get another supplier. It was Mamiya's choice not too.

I expect that Mamiya specifically requested a shutter that would open and close automatically, and then not re-open until the camera was re-cocked. The T function is a very simple addition - it just blocks the shutter from closing down again, until you move the shutter speed dial off T.
Adding a separate shutter release and cocking mechanism just for the T exposures wouldn't have made a lot of sense, when a simple movement of the shutter speed dial accomplishes what you need.
The mechanisms used in the RB67 to both cock and control the leaf shutters at the end of the bellows and protect and advance the film are actually quite elegant in their simplicity and robustness.

 

[Alan Edward Klein]

I expect that Mamiya specifically requested a shutter that would open and close automatically, and then not re-open until the camera was re-cocked. The T function is a very simple addition - it just blocks the shutter from closing down again, until you move the shutter speed dial off T.
Adding a separate shutter release and cocking mechanism just for the T exposures wouldn't have made a lot of sense, when a simple movement of the shutter speed dial accomplishes what you need.
The mechanisms used in the RB67 to both cock and control the leaf shutters at the end of the bellows and protect and advance the film are actually quite elegant in their simplicity and robustness.

I've owned an RB67 for thirty years and agree that it's awkward to shut down the shutter in T mode. It would have been better to let's say have another click on the cable release would have done it. But I suppose the complicated way the RB67 operates made this too difficult to do. How does Hasselblad handle it?

 

[MattKing]

How does Hasselblad handle it?

Hasselblad doesn't have to deal with there being a bellows between the camera body and the shutter containing lens.

 

[Alan Edward Klein]

Hasselblad doesn't have to deal with there being a bellows between the camera body and the shutter containing lens.

I don't understand what that means. Can you explain its operation?

 

[MattKing]

I don't understand what that means. Can you explain its operation?

Think of the differences between the cameras.
The Hasselblad has a solid connection (the lens mount) between the camera body and the lens (which contains the shutter). It is relatively easy to build a fixed shutter cocking mechanism and safety interlocks into that construction.
The Mamiya puts a bellows between the lens mount and the camera.
All the safety interlocks are essentially fixed in place with the Hasselblad.
The interlocks and lens cocking mechanism on the Mamiya have to deal with a bellows that moves and may extend out 200mm or more for the longer lenses. The way that is accomplished is that when the shutter is released, the mirror flips up, which triggers the opening of the shutter. That mirror doesn't come down again until the side lever is actuated, which is the action that also cocks the shutter.
Normally, the RB67 shutter closes automatically at the end of the exposure, leaving the mirror still up, and the film still open to the inside of the camera. When you engage the T function, the shutter stays open, until one either moves the shutter speed selector off the T setting, or the shutter is re-cocked.
With the mirror up, there is no connection between the shutter release and the shutter - nothing (on the camera, not the lens) that you could press to make the shutter do something.
Mamiya could have elected to add a separate shutter release to the T function on every lens, but they didn't.

 

[Sirius Glass]

I've owned an RB67 for thirty years and agree that it's awkward to shut down the shutter in T mode. It would have been better to let's say have another click on the cable release would have done it. But I suppose the complicated way the RB67 operates made this too difficult to do. How does Hasselblad handle it?

Think of the differences between the cameras.
The Hasselblad has a solid connection (the lens mount) between the camera body and the lens (which contains the shutter). It is relatively easy to build a fixed shutter cocking mechanism and safety interlocks into that construction.
The Mamiya puts a bellows between the lens mount and the camera.
All the safety interlocks are essentially fixed in place with the Hasselblad.
The interlocks and lens cocking mechanism on the Mamiya have to deal with a bellows that moves and may extend out 200mm or more for the longer lenses. The way that is accomplished is that when the shutter is released, the mirror flips up, which triggers the opening of the shutter. That mirror doesn't come down again until the side lever is actuated, which is the action that also cocks the shutter.
Normally, the RB67 shutter closes automatically at the end of the exposure, leaving the mirror still up, and the film still open to the inside of the camera. When you engage the T function, the shutter stays open, until one either moves the shutter speed selector off the T setting, or the shutter is re-cocked.
With the mirror up, there is no connection between the shutter release and the shutter - nothing (on the camera, not the lens) that you could press to make the shutter do something.
Mamiya could have elected to add a separate shutter release to the T function on every lens, but they didn't.

When a Hasselblad uses bellows, use a double cable release to handle the coordination.

 

[Donald Qualls]

Mamiya could have elected to add a separate shutter release to the T function on every lens, but they didn't.

But they do have a separate shutter release on each lens -- it's used to fire the shutter after using the mirror prefire (which disengages the mirror-triggered release from the actual shutter). If the shutter had been designed with a true T, a second actuation of that release would close the shutter (whether mirror prefire was in use or not).

 

[MattKing]

But they do have a separate shutter release on each lens -- it's used to fire the shutter after using the mirror prefire (which disengages the mirror-triggered release from the actual shutter). If the shutter had been designed with a true T, a second actuation of that release would close the shutter (whether mirror prefire was in use or not).

It actually isn't a release - it is a stop that prevents the shutter from releasing, until you depress the attached cable release.
I know this seems like semantics, but the entire system is designed for actuation via the mirror, not via the shutter release per se. Just as the shutter is designed to close automatically after the exposure and to stay closed until the mirror is lowered. The T function is essentially a stop as well. And all of that design flows from there being a bellows between the body and the lenses.

 

[Grim Tuesday]

Who makes the shutter for late Fuji cameras? They also have the same stupid "T" functionality where you need to cock the shutter to close it. Even stranger, it's not a shutter speed on the ring that you can set and use with the cable release, it's a separate button you have to push with a toothpick! At least they come with self timers for starting it without vibration but it's such a head scratcher why they didn't just use a normal bulb mode

 

[wiltw]

Who makes the shutter for late Fuji cameras? They also have the same stupid "T" functionality where you need to cock the shutter to close it. Even stranger, it's not a shutter speed on the ring that you can set and use with the cable release, it's a separate button you have to push with a toothpick! At least they come with self timers for starting it without vibration but it's such a head scratcher why they didn't just use a normal bulb mode

The shutter is by Seiko. in teh GX680-II and GX680-III. Both have B, not T. Are you referring to Fuji digital medium format? There is little to no mention of the shutter design nor manufacturer.

The Seiko electronic shutters have T in order to preserve battery life for long-duration exposure.

 

[Grim Tuesday]

The shutter is by Seiko. in teh GX680-II and GX680-III. Both have B, not T. Are you referring to Fuji digital medium format? There is little to no mention of the shutter design nor manufacturer.

The Seiko electronic shutters have T in order to preserve battery life for long-duration exposure.

I should have been more specific but I was thinking of the rangefinders, which have mechanical shutters. An interesting exception is the GA645Zi which has true bulb mode and an electronic shutter!