Bulb mode on Mamiya KL lens not working properly

Meerkieker · Aug 28, 2017

Hello folks

I'm trying for the first time to set the BULB mode on my KL lens but for some unknown reason i can't get it to work.

Basically i turn first the shutter on T mode, then plug my mamiya double cable release on both the shutter release and B socket (Available only on KL lenses). I then cock both mirror and shutter and press the release. Result? The shutter stays open and in order to end my exposure i'm forced to either move shutter time to 1s or slightly moving forwards my cocking lever. I thought that the shutter had to stay open as long as i depressed the release but that seems not to be my case for some reason.

Similarly even on MUP mode, the same issue appears again. Here what's stated in the manual:

When exposure is longer than 1 second, it is convenient to integrate with time(T):
(1) Screw the short mirror release cable into the bulb unit of the lens, and screw the long cable into the mirror lock-up socket.

(2) Set the shutter speed ring to T.

(3) Raise the mirror by pressing the shutter release button on the body. (4) The first stroke of the mirror release will open the shutter and the second stroke of the mirror release will close it.

With my double release cable nothing happens again on the second stroke, shutter stays open and i'm forced to turn shutter time to 1.

Am i messing something up or is my lens defect?

Many help in advance for any given explanation .

Sirius Glass · Aug 28, 2017

Usually T opens the first time the shutter is tripped and closes when the shutter is tripped again. B stays open as long as the shutter is held open.

Meerkieker · Aug 28, 2017

Sirius Glass said:
Usually T opens the first time the shutter is tripped and closes when the shutter is tripped again. B stays open as long as the shutter is held open.

That´s how its supposed to go indeed, but as already stated, not in my case. I really can´t get it..

WilmarcoImaging · Aug 29, 2017

Einen schönen guten Tag Meerkieker

I tried this on my Pro SD with 90mm KL lens and it works:

1. Cock the body and shutter, set the shutter to T, thread the *MAIN* cable release into the B socket. Do not use the secondary (MLU) release pin. It is too short by 1mm, at least on my double cable release.

2. Fire the shutter with the normal silver button. Do this with your finger or with a second, normal, cable release. The shutter is now open.

3. Press the cable release connected to the B socket. The shutter should close. It did on my camera.

The reason this can't be done with the Mamiya dual cable release (I have one), is the way the two pins are mechanically sequenced. The primary pin is longer and actuates first. The longer pin is needed in the B socket, but the B socket needs to be actuated last, after the mirror is up and the shutter is open.

This may be a situation where tiny differences in tolerances allow you to use the double cable release. But in my case, and it seems in your case, two separate cable releases are needed. Or use your finger to open the shutter and one cable release to close the shutter.

I checked the Pro SD manual and there is nothing written on this. The C-lens instructions for MLU are provided in the Pro SD manual, yet the first pages of the Pro SD manual refer to KL lenses.

WilmarcoImaging · Aug 29, 2017

Here is the Pro SD manual: http://www.butkus.org/chinon/mamiya/mamiya_rb67_pro_sd/mamiya_rb67_pro_sd.htm

On page 28 it is written: "To make a time exposure, first set the shutter speed ring to T and screw a cable release into the bulb socket. After doing so, the shutter will remain open upon depressing the shutter release button. The shutter will be closed by pressing the plunger of the cable release without giving any shock to the camera. The shutter can also be closed by the following procedures..." [please see manual for further info]

Following the above procedure exactly, it works. Using the Mamiya double cable release is not possible because of the nature of how it works. The secondary pin is shorter and deploys later than the primary pin. Reversing the pins does not work, and using them in the primary/secondary orientation doesn't work, because the secondary pin is too short for the bulb feature.

Doing a time exposure with minimum shock to the camera is done with 2 separate, individual, cable releases. One on the main (silver) release button and one on the Bulb socket on the lens.

Time exposures with KL lenses can also done by first pressing the main silver release button, and then,
- turning the shutter speed ring to another setting, or
- pressing the bulb socket with a finger, or
- moving the cocking lever by approximately 30 degrees

See page 28 of the manual for the above description.

Meerkieker · Sep 2, 2017

WilmarcoImaging said:
Here is the Pro SD manual: http://www.butkus.org/chinon/mamiya/mamiya_rb67_pro_sd/mamiya_rb67_pro_sd.htm

On page 28 it is written: "To make a time exposure, first set the shutter speed ring to T and screw a cable release into the bulb socket. After doing so, the shutter will remain open upon depressing the shutter release button. The shutter will be closed by pressing the plunger of the cable release without giving any shock to the camera. The shutter can also be closed by the following procedures..." [please see manual for further info]

Following the above procedure exactly, it works. Using the Mamiya double cable release is not possible because of the nature of how it works. The secondary pin is shorter and deploys later than the primary pin. Reversing the pins does not work, and using them in the primary/secondary orientation doesn't work, because the secondary pin is too short for the bulb feature.

Doing a time exposure with minimum shock to the camera is done with 2 separate, individual, cable releases. One on the main (silver) release button and one on the Bulb socket on the lens.

Time exposures with KL lenses can also done by first pressing the main silver release button, and then,
- turning the shutter speed ring to another setting, or
- pressing the bulb socket with a finger, or
- moving the cocking lever by approximately 30 degrees

See page 28 of the manual for the above description.

Moin,

You´ve been really helpful clarifying that issue regarding the double cable release. Actually i tried what you said, that is reversing the pins, but on a second glance i thought that the pins must have been too short for any positve effect to take place. The sequential trigger of the pins sure have their role as you state. Sounds like i have to get rid of that trigger and get two separate cable releases.. are all of them standard size?

regarding the last part of your second post, i screwed the silver pin into the shutter, put in t mode, tripped the shutter. then to close the shutter i pushed the bulb socket with my finger as stated in the manual, but nothing happened. What might be the cause?

Danke sehr

WilmarcoImaging · Sep 3, 2017

Hallo wieder Meerkieker

When you push the small silver ring on the bulb socket, it closes the shutter on my 90mm KL lens when the shutter speed ring is in "T" and the shutter has been released normally.

Try it with a small tool, because the movement of the "B" socket button is very small. It sounds like this feature on the KL lenses is sensitive to assembly tolerances. Some lenses could give good performance and some lenses could need some adjusting.

BItte im jeden Fall schreiben Sie mir einem PM wenn gewünscht.

WilmarcoImaging · Sep 3, 2017

Hi again Meerkieker

I tried again with my Pro SD and 90 KL lens. It works easily every time:

1. Cock body and lens as normal
2. Set shutter speed to T
3. Fire body/shutter with silver button on the body, as normal. Shutter is now open.
4. Press with a finger the small silver B button on the lens. Shutter is now closed.
5. Cock the body and lens as normal.

Bulb mode on Mamiya KL lens not working properly

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