Question about DBM mount

[Songyun]

Does DBM has auto aperture feature? I tried to trigger the shutter, but it doesn't work.

[mikec]

hmm. By DBM are you talking about the Sinar boards? These are auto with a manual override, the auto aperture feature being actioned by either a red button or a sort of latch. In order for them to work as auto aperture, the latch/red button has to be in the UP/OUT position respectively AND they have to be used in conjunction with the Sinar Copal shutter board. In order for the ergot on the shutter to be able to action the auto aperture mechanisn, the red dot on the inner face of the board also has to be aligned with the red dot on the shutter face. The required aperture for auto operation is selected on the shutter board . The DB/DBM lens boards do not affect the shutter operation AFIK. At least if installed correctly. Hope that helps. If not give a bit more detail of your issue.

[Sevo]

DBM are auto aperture with sinar BTL shutters, with manual aperture override, DB are auto only - that is, without a sinar shutter, DBM work like any barrel lens (by switching to manual), but DB only work wide open.

Jammed DB(M) lenses can block some, but not all shutters, but otherwise the mechanism is transparent and you can use other barrel or shutter mounted lenses in front of a sinar shutter as long as they don't protrude into the shutter leaves.

Does the shutter work by itself? And do you have a release cable? The sinar shutters have no shutter trigger except for the (mechanical or electronic) special release cable. The red lever and release switch on the sinar/Copal shutter are merely opening respectively closing the shutter for preview, at fully open aperture regardless of the setting - to temporarily stop down while previewing, push the cable release.

Sevo

[Songyun]

I used a sinar shutter with cable. when I turned the dial on the shutter to something smaller than the dial on the lens ( for example, if I set f8 on the lens with the red button, and set f11 on shutter) the shutter can not push the aperture to f11. I will take another look tonight, when I get back home.

[Sevo]

At least with the older slider-coupling DBM mount, the shutter side aperture setting is entirely out of effect when the lens is on manual override, as the aperture lever on the rear of the lens gets uncoupled by the slider.

Sevo