If your RB back operates anything like my RZ, you may find that installing the darkside only when it is needed "may" save your some grief one day. When I first bought my RZ, I was removing and installing the darkside each time I used the camera. One day I picked up the camera and the back fell off the camera. Luckily I caught it on the way down. The cause . . . The latch on the bottom of the film back wiggled over time to the unlocked position. With the darkside installed, there was nothing to hold the back onto the camera.
The previous owner said that in his opinion the RB ProSD has no darkslide lock at all. I didn't check with the manual yet but I will.
Not sure what you mean by this.
If you mean that the dark slide can be pulled out at any time, that is wrong - the back must be on the camera, or the little pin must be manually pressed.
If you mean that the shutter can be released even if the dark slide is in, the manual says:
"The shutter release button can not be depressed if the dark slide is completely inserted or if here is no film in the camera. In addition the Pro-SD roll film coupler prevents multiple exposures. (See pages 16 and 25 for the shutter release test.)"
It may be the case that if you have a dark slide from an earlier version of the camera (RB67 Pro or Pro-S) that the dark slide exposure prevention interlock won't function. IIRC, that is what happens on my Pro-S when I insert a Pro dark slide.
“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”
Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2
I thought I can make it clearer when i show pictures.
A is the hole in the body where I can see a pin moving when pressing the shutter. The pin doesn't stick out when firing.
B shows the little hole in the rotating part which matches with the hole A on the body.
C is the little piece which moves when pushing in the dark slide completely
D is the part of the dark slide which speakes to the whole locking mechanism.
Since A never sticks out there is no connection between the locking mechanism of the darkslide/rotating part/back and the body.
I think A is meant to stick out to make it possible that the shutter is locked when the darkslide is fully in.
With back removed looking from rear of camera towards the lens with rotating adapter in landscape there are two chrome knobs
The right hand one is the shutter firing pin which is blocked by a back when the back is not able to fire this inhibits the shutter button depressing.
The left hand one tells the back that the mirror has finished its travel. Don't block it it is an instantaneous out and in you can just see it travel if you are careful. This pin tells the back to block the shutter release from depressing again until the back is wound on.
The dark slide overrides the logic.
An earlier camera, rotating adapter or back won't have all the logic they are still usable...