I've just purchased a Mamiya RB67 ProS camera (fulfilling a long standing dream to own and use a medium format SLR). It came with a 90 mm f/3.8 Mamiya-Sekor C lens, and two 120 film backs, one for 6x4.5 and one for 6x7 cm. As far as I can tell without having shot and processed a roll yet, everything appears to work correctly.

I found a YouTube video recently showing "how to" shoot long exposures (longer than 1 second) -- which is different from most other cameras and lenses I've used (since 1970). The "common" way is to mount the camera on a sturdy tripod (or similar steady support), set the shutter to "B", and use a locking cable release to open the shutter and hold it open for the required time, then unlock the release to close the shutter.

The RB67, however, has only "T" shutter above "1", no "B" setting. I'm used to "T" meaning the shutter will open when I press the release, and close when I press again, but in the RB67, the shutter opens and then the shutter release locks. Recocking closes the shutter, and the only other way I've found to close the shutter (based on a YouTube video) is to turn the shutter speed ring off the "T" setting. This works the same way whether I set the "mirror up" release on the shutter, and trip the shutter with it, or if I try to do everything with the release on the body.

The same video told me I'd otherwise need a dual cable release to use the "T" setting for long exposures. However, I haven't found any information (so far) about how to actually use the dual cable release, either with or without the mirror pre-fire, to shoot long exposures on "T" with the RB67. I don't yet have such a release, but my attempts to simulate using both releases in "T" have resulted in the same results the video maker had -- having to turn the speed ring off "T" or cock the body to close the lens.

  • 1
    FWIW you don't need a dual cable release. You can use 2 single cable releases and press them in the correct order. This is my fav. youtube video on the RB. I'd make this a real answer but I'd be working from memory from when I only used an RB for 2 weeks, 3 months ago.
    – Peter M
    Mar 8, 2020 at 13:13
  • Thanks, @PeterM -- I'd viewed the first segment of that tutorial, but only the first couple minutes of the second because it looked like he was just covering the obvious stuff. Now I know about the exposure compensation calculator, too.
    – Zeiss Ikon
    Mar 8, 2020 at 22:52
  • Well that all depends on your definition of "obvious". For me the videos by that guy covered the complete features and operation of the RB, although his second video (the one I linked to) seemed to cover the more practical aspects.
    – Peter M
    Mar 9, 2020 at 12:42

3 Answers 3


I've had my RB67 Pro for a few years now, and have occasionally done long exposures using two separate cable releases. Mamiya's double cable release is no different, as it is virtually a 2-in-1 cable release. You may as well use a hairpin to set off the shutter when the lens is in mirror up mode.

So, unfortunately, the only way to close the shutter in T mode is to either turn the shutter speed ring, or by advancing the cocking lever on the side of the body. This is regardless of whether you are or are not using two cable releases. If you're afraid of moving the camera doing this, I recommend covering the lens with a lens cap to prevent any motion blur from you touching the camera.

  • Wow. All the careful thought that went into this camera, and they couldn't come up with a way to automatically close the shutter after a long exposure. Black hat or lens cap it is (if you're doing long exposures with light sources in frame, they'll make trails from movement if you try to close the lens with the body cock lever or speed setting ring). Don't even really need a cable to trigger the mirror in lock-up mode...
    – Zeiss Ikon
    Mar 8, 2020 at 22:55
  • I totally agree and wish they had opted in for bulb mode or that you could close the shutter by firing it off a second time. My Nikon F3 works the same way, unfortunately.
    – timvrhn
    Mar 9, 2020 at 8:22
  • Of course, there's also the option to use my Speed Graphic and the (620) roll holder I have for it (with a made-up 6x7, 6x6, or 6x4.5 mask if I don't want to shoot 6x9) for night shots. That has two shutters (leaf and focal plane) that work the way everyone expects. It may even weigh less (built of wood, not cast metal).
    – Zeiss Ikon
    Mar 10, 2020 at 11:20

As Mark R. said, and btw thank you, that's the way bulb mode works in the C lens I own (65mm & 127mm), they both have the 'B slot', which is right besides the PC sync for flash. I am now finally able to do bulb mode in my RB67, using 2 cable releases.

Just check if the lens you're wanting to buy has the B slot, I am looking into buying a C 180mm, and it does not have the B slot for bulb. The 180mm K/L model has it.

So apparently some C lenses have the B slot, and some don't.

  • All of my lenses (currently 50 mm, 90 mm, and 250 mm) have a cable release socket with the N and T setting collar (pull and turn to set). None have a B option.
    – Zeiss Ikon
    May 27, 2021 at 11:07

After watching all the YouTube videos as well as reading all the blog posts. And eventually reaching the conclusion that answer doesn’t exist online. I turned to the Mamiya manual and after some trials and errors I figured it out.

The question is how to shoot long exposure (T) while using lock up mirror function without touching your camera.

It must be noted that this is how it works on my Mamiya RB67 Pro SD and a KL 127mm lens, so it might be different on a pro S and C lenses.

I use a Mamiya dual cable however it is possible with two separate cables.

  1. Screw the #1 cable into mirror up slot ( the number one is the one that releases further and at any pressure of the button)
  2. Screw the #2 cable into B slot on the lens (the two is the one that starts ejecting after half press)
  3. Cock the shutter. Press the release on your body (locks up the mirror)
  4. Half-press the cable release (opens the lens shutter)
  5. Fully press the cable release button to close the shutter. (Doesn’t have to be kept half-pressed between the two)

This gives you the usual feel of bulb modes on other cameras.

The B button can also be pressed with your finger to close the shutter. ( however you are touching the lens and might as well press on the lever slightly, approximately same amount of shake if not more than later)

Obviously this can be done with two cables instead of half pressing on a dual one.

Also ( which is an overkill but you can use three cables and never touch your camera after cocking it all together, hence one cable for body, two cables for lens).

Hope this helps. Let me know if this works on C lenses as I’m looking to pick up 50mm and as far as I know they don’t exist in KL version.

  • There is no "B" slot on Sekor C lenses (which are all I own). I now own 50, 90 and 250 lenses, all work the same way: lens has T only, no B, and the only way to close the shutter after a T exposure is to recock the body. This works with a single cable release.
    – Zeiss Ikon
    Feb 3, 2021 at 18:59

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