A little known accessory for Leica screw mount cameras is the VACU. It was made in a variety of versions. It offered the use of flash equipment with Leica cameras up to the Leica IIIc. Its replacement, the Leica IIIf was the first model with built-in flash synch.
Leitz made several versions, all with their own catalog designation. Ranging from CAVOO-A to CAVOO-F.
The CAVOO-A was to be used with the Leica III, the CAVOO-B was for the Leica IIIa and IIIb and several versions for the "c" model Leicas, from CAVOO-C to CAVOO-F.
The unit consisted of a small trigger device that screwed onto the shutter release of the camera. It worked in conjunction with a small cam that attached to the shutter release dial. When releasing the shutter, the rotating shutter speed dial would activate a small switch via the cam to fire the flash. This in turn was connected to the VACU via a short cord with a PC fitting.
The cam attachment came in four different versions depending what model Leica it was for. A word of caution; I have seen versions of the VACU offered for sale from time to time, but in each case the cam was missing, therefore rendering the unit incomplete and useless.
Cam attached to shutter speed dial
The position of the cam on the shutter speed dial is critical because it determines the position of the shutter curtains at the moment the flash is triggered. Rotating it back or forth will allow for exact positioning.
That, of course, requires a means to see if the flash is fired at the correct moment. For this there is a very simple solution as explained in the article “TESTING LEICA SM CAMERAS FOR PROPER FLASH SYNCH” from March 8, 2012 on this blog.
VACU on Leica III Front View
VACU on Leica III Rear View
The first Leica I ever owned, a Leica III, was equipped with a VACU. I still consider it one of my prized possessions and I fondly remember leaning to take pictures with this camera, including flash pictures. It is a great camera to learn with because everything is manual. It created useful habits that I still practice today. For instance, after getting many severely blurred pictures, in spite of careful focusing, I learned that it is advisable to pull out the collapsible Summar f/2 before shooting.
Leica III with VACU
But that is ultimately a different story. I don’t use the Leica III very often anymore in these days of digital photography. But it does take up a prominent spot in my Leica collection, together with the VACU attachment in place on the camera.