Mamiya RB67, 250mm f/4.5C, Blank Frames

[rwreich]

Hello All,

I believe that my 250mm f/4.5C lens for the RB67 was malfunctioning because I have blank frames on several rolls of film shot at different times. In order to check the problem, I took the back off and fired the shutter a few times to determine whether I could see any light passing through. At first, I wasn't sure that I saw anything. I'm almost certain that I did not see anything.

I looked on the lens barrel and noticed a knob that switched from mode N to mode M. I am just guessing that N is for normal and M is for mirror lock-up. If the knob were switched to M, would that be the cause of the blank frames? Or - do you have to actually have the cable-release in the socket in order to activate the lock-up?

Once I switched it to N mode and tested slower shutter speeds, I can now see light passing through the lens (while attached to the body with no back) at all shutter speeds.

Do I need to have the lens CLA'd, or was it just that knob in the wrong spot? Could it be something totally different?

Thanks in advance!

- Wayne

 

[Theo Sulphate]

Yah! When it's on M, pressing the body release locks the mirror up. To actually trip the shutter in that case, you'd attach a cable release to the lens.

BTW, for that lens, the 360, and the 100-200, I think you should have a mount bracket so as not to bend the focus rails.

 

[rwreich]

Okay - I should have known better. Oh well :-/

You really think that lens is big enough to warrant a bracket? I'll look into it...

 

[tedr1]

Yes the M setting permits shutter firing only via the side connection. After the "exposure" because the shutter resets when cocked in the normal way you never know it didn't fire :-( On some (later?) lenses the printed M is replaced by "MIRROR UP" on the lens body.

 

[rwreich]

Yes the M setting permits shutter firing only via the side connection. After the "exposure" because the shutter resets when cocked in the normal way you never know it didn't fire :-( On some (later?) lenses the printed M is replaced by "MIRROR UP" on the lens body.

On my K/L lenses, the mirror-up function only works when the cable release is inserted into the socket. I don't know why I didn't double check... In the moment, it seemed like it was working. Lesson learned!

 

[clingfilm]

BTW, for that lens, the 360, and the 100-200, I think you should have a mount bracket so as not to bend the focus rails.

Just saw this and now you've got me worried about using my 250 - anywhere where I could find one of these things?

 

[paul ron]

the 250 doesnt really need the support bracket. ive used mine without any problems.

the cable is needed to fire the shutter after the body is fired... mirror is up, shutter will be on stand by. recocking the camera n lens will leave a blank frame if the shutter was never fired.

just be sure the shutter fires when in Normal mode... test with the back open to see it open n close properly.

 

[clingfilm]

the 250 doesnt really need the support bracket. ive used mine without any problems.

the cable is needed to fire the shutter after the body is fired... mirror is up, shutter will be on stand by. recocking the camera n lens will leave a blank frame if the shutter was never fired.

just be sure the shutter fires when in Normal mode... test with the back open to see it open n close properly.

Ah phew.. Yeah, the mirror up mode actually makes it quite a stealthy camera >.>

 

[Alan Klein]

I have a 360mm and haven't noticed any problems with the focusing rail. What does the manufacturer recommend?

 

[Theo Sulphate]

The 100-200, comes with a bracket and that lens weighs 1620gr.

The 250 and 360 (depending on version) are a few hundred grams lighter. So, I suspect they're ok. The 500mm needs a bracket.

Sorry for causing worry.