RB67 "T" Exposure Question.

ChristopherCoy · Mar 19, 2021

With regards to the "T" or time settings on the RB67 lenses - is there no other way to close the shutter besides having to cover the front element and use the shutter cocking lever?

I've been watching a particular photographer on youtube, and when doing a long exposure, he uses the shutter cocking lever on the side of the camera to close the shutter. As a safeguard he covers the front element with his hand to prevent any blurring. Is there no other way to close the shutter? Shouldn't it just close when you let go of the cable release?

Or is "T" not the same as "bulb"?

Donald Qualls · Mar 19, 2021

I asked the same question when I got mine.

Short answer: no, there's no other option.

You need to set the lens to the "mirror up" setting and use a cable release to fire the shutter from the lens to get even that, as I recall (I haven't used this on mine since testing it the week the camera arrived). You prefire the body (to raise the mirror), then fire the shutter via the cable release (or poke a paper clip into the socket on the shutter). When done, cover the lens with a lens cap, black had, etc., then turn the speed ring or recock the body to close the shutter.

It has never made any sense to me why Mamiya chose to do it this way rather than use B like everyone else; Seiko, who made the shutters, also made large format shutters that offered both B (open for as long as you hold the cable) and T (open on actuation, close on next actuation) or approximately equivalent "open focus" setting.

ChristopherCoy · Mar 19, 2021

Yeah, I tried it on mine a few days ago. I thought I had gotten myself into all kind of trouble because I did it without a cable release on the lens, and then I couldn't get it closed. Turns out the back had inadvertently gotten slightly rotated just enough to prevent the lever from going forward. Bout freaked out when that happened.

Not that it's extremely difficult to cover the lens and use the lever or speed ring, it just introduces a lot of room for error or vibration to occur, which is exactly what you're trying to avoid.

MattKing · Mar 19, 2021

Most likely they work the way they do because when used normally, the shutter in the lens closes at the end of the exposure, and doesn't re-open until you use the side of the camera cocking lever.
When set to T, there is nothing to trigger the closing, except changing the shutter speed or using the side mounted cocking lever.

MattKing · Mar 19, 2021

Use a black baseball cap to cover the lens at the end of the time, then move the shutter speed indicator.. If your exposure is longer than one second, light levels at the film plane are so low that the tiny amount of variance in time or vibration at the end won't result in any appreciable change.

ChristopherCoy · Mar 19, 2021

MattKing said:
Use a black baseball cap to cover the lens at the end of the time, then move the shutter speed indicator.. If your exposure is longer than one second, light levels at the film plane are so low that the tiny amount of variance in time or vibration at the end won't result in any appreciable change.

I know. It would have just been nice if it would close when you let go of the cable release, or with a subsequent click of the shutter. I can just see myself going to place the hat/cap/hand in front of the lens and knocking something around because I'm just that graceful.

Andrew O'Neill · Mar 19, 2021

If you change the shutter speed during the exposure, it will terminate close the shutter. I had to do this once out on a shoot because the shutter would stay open during exposures longer than one second. I wouldn't recommend doing this all the time, as it is probably hard on the mechanisms.

Donald Qualls · Mar 19, 2021

MattKing said:
Use a black baseball cap to cover the lens at the end of the time, then move the shutter speed indicator.. If your exposure is longer than one second, light levels at the film plane are so low that the tiny amount of variance in time or vibration at the end won't result in any appreciable change.

While true for things like "night for day" exposures, if there are light sources (streetlights, holiday decorations, neon, etc.) in frame they'll trail with the slightest vibration. This makes mirror prefire a good technique even if it's not strictly required, and promotes black-hatting before closing the shutter.

wiltw · Mar 19, 2021

Bronica, which used Seiko electronic shutters, had a T setting on its lenses so that continuous battery consumption (during B) could be avoided on very long exposures.
I cannot say what the reason would be in a purely mechanically timed shutter though. Dan Quall's explanaiton of T for 'open to focus' on large format cameras makes sense, though. But Alan Klein's included instructions make that particular example (large format focusing) not really terrific implementation.

Alan Edward Klein · Mar 19, 2021

T shutter operation from RB67 manual

Maris · Mar 19, 2021

Over the years I've done some hundreds of T exposures with the Mamiya RB67 and have not yet seen camera shake.
Reason one is that the camera is on a good tripod and the act of pushing the cocking lever to terminate the exposure pushes the camera towards the tripod - in the direction of maximum stability.
Reason two is if I get a metered exposure indicated at two seconds I'll stop down and change the exposure time to four seconds. Any momentary camera movement is too small a proportion of the overall time to register on the film.

ChristopherCoy · Mar 19, 2021

Maris said:
Reason two is if I get a metered exposure indicated at two seconds I'll stop down and change the exposure time to four seconds. Any momentary camera movement is too small a proportion of the overall time to register on the film.

Even with something like a street lamp or neon sign?

MattKing · Mar 19, 2021

ChristopherCoy said:
Even with something like a street lamp or neon sign?

That's why you first put the baseball cap over the lens.

ChristopherCoy · Mar 19, 2021

MattKing said:
That's why you first put the baseball cap over the lens.

I understood that, but I wanted to see what his experience and opinion was.

Maris · Mar 19, 2021

ChristopherCoy said:
Even with something like a street lamp or neon sign?

Moonrise and Boats, Noosa River
Gelatin-silver photograph on Ilford Classic VC FB photographic paper, image size 16.3cm X 21.5cm, from a Kodak Tmax 400 negative exposed in a Mamiya RB67 camera fitted with a 360mm f6.3 lens. Two seconds at f11.

Normally I'd try for a four second exposure, it would have been easier to time, but even on a still evening the water would have lost texture and the moon could show motion blur. The movement of the RB67 cocking lever is relatively light in the first part of the stroke, that's where the shutter is closed, and gets heavier at the end when the reflex mirror is pushed down and the shutter is cocked.

Alan Edward Klein · Mar 19, 2021

I haven't taken that many 2 sec shots. But I haven't noticed any blur when I release the T shutter settings when used. I haven't used the hat trick. But I'd probably slap the lens with it and move the whole setup.

ChristopherCoy · Mar 19, 2021

Nice Maris!

Alan Edward Klein · Mar 19, 2021

Maris said:
Moonrise and Boats, Noosa River
Gelatin-silver photograph on Ilford Classic VC FB photographic paper, image size 16.3cm X 21.5cm, from a Kodak Tmax 400 negative exposed in a Mamiya RB67 camera fitted with a 360mm f6.3 lens. Two seconds at f11.

Normally I'd try for a four second exposure, it would have been easier to time, but even on a still evening the water would have lost texture and the moon could show motion blur. The movement of the RB67 cocking lever is relatively light in the first part of the stroke, that's where the shutter is closed, and gets heavier at the end when the reflex mirror is pushed down and the shutter is cocked.

Nice shot Maris. Tell us you shot this from the deck of another boat.

Sirius Glass · Mar 20, 2021

'T' shutter works thusly:

Cock shutter
Fire shutter to open
Fire shutter to close

That is the technical description of how a T shutter works.

wiltw · Mar 20, 2021

Sirius Glass said:
'T' shutter works thusly:

Cock shutter

Fire shutter to open

Fire shutter to close

That is the technical description of how a T shutter works.

Unfortunately, Mamiya RB 67 instructions state otherwise...

"2. To close the shutter, turn the shutter speed ring towards the 1 sec. mark, or press down the shutter cocking lever about 30 degrees"

It goes contrary to what you or I had learned about the use of 'T' on a camera.

Sirius Glass · Mar 20, 2021

wiltw said:
Unfortunately, Mamiya RB 67 instructions state otherwise...

"2. To close the shutter, turn the shutter speed ring towards the 1 sec. mark, or press down the shutter cocking lever about 30 degrees"

It goes contrary to what you or I had learned about the use of 'T' on a camera.

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

MattKing · Mar 20, 2021

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

They are the industry standard - for bellows mounted interchangeable lens 6x7 SLRs.

Alan Edward Klein · Mar 20, 2021

Mamiya should have called it their Q shutter for their RB67's T mode.

Maris · Mar 20, 2021

Alan Edward Klein said:
Nice shot Maris. Tell us you shot this from the deck of another boat.

No boat. Shot from the Doonella bridge. Waited until there were no cars passing to avoid "bridge shake".

wiltw · Mar 20, 2021

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

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.

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