monopix
Cam repairer
I've never yet found a description of the way the double shutter on the Bessa cameras is constructed. All references seem to suggest it's a shutter with a double layer curtain. Stephen describes it as a 'Modified Copal shutter with two sets of blades' on his page here. Well I had the chance to dismantle a Bessa L recently and I can say this is definitely not a modified Copal shutter. In fact, it's two separate shutters with the main one (the rear one) being a standard Copal shutter as used in a trillion other cameras and not just ones made by Cosina. The second shutter, the front one, is completely separate and works, in principle, in the same way as a mirror does in an SLR - which makes sense because it's taking the place of the mirror in blocking light getting to the shutter.
The second shutter is built on to the back of a central box, very similar to the mirror box on an SLR, which has the lens mount attached to the front. The shutter is cocked separately and is linked to the main shutter using the same linkages as would be used to link the mirror and the shutter in an SLR. And the function is the same as a mirror in that, when the shutter release is pressed, the second shutter is triggered. As it fully opens, it triggers the main shutter which, in turn, triggers the second shutter to close after the exposure. This is identical to the sequence that takes place in an SLR between mirror and shutter.
It's actually a very neat way of achieving what was required.
The second shutter has no manufacturer's mark and I guess it's a Cosina design and they manufactured it.
bessa shutter 1 by Peter Robinson, on Flickr
bessa shutter 2 by Peter Robinson, on Flickr
The second shutter is built on to the back of a central box, very similar to the mirror box on an SLR, which has the lens mount attached to the front. The shutter is cocked separately and is linked to the main shutter using the same linkages as would be used to link the mirror and the shutter in an SLR. And the function is the same as a mirror in that, when the shutter release is pressed, the second shutter is triggered. As it fully opens, it triggers the main shutter which, in turn, triggers the second shutter to close after the exposure. This is identical to the sequence that takes place in an SLR between mirror and shutter.
It's actually a very neat way of achieving what was required.
The second shutter has no manufacturer's mark and I guess it's a Cosina design and they manufactured it.
bessa shutter 1 by Peter Robinson, on Flickrbessa shutter 2 by Peter Robinson, on Flickrvaldas
Mentor
I hope very much it’s not the Bessa you bought from me 
monopix
Cam repairer
Oh hi Valdas. No, it's not that one. This is a Bessa L that came to me in non-working condition. Hopefully it will be working once I finish with it.
charjohncarter
Mentor
I'm not sure I understand the purpose of the second shutter. Could you explain? I get the mirror substitute but why?
valdas
Mentor
I guess the same design is in other Bessas as well? I think I had an issue with R2A that when the battery was really low it still kept on firing, but only one set of blades was opening (that is my guess). So, I hear the click, all seems fine, but then I develop the film and boom - blank frames on the half of the roll..
Freakscene
Obscure member
The main Copal shutter is not 100% light tight because it is designed to have an SLR mirror in front of it. So the additional shutter is essentially a blind to stop the film from being incidentally exposed while the rangefinder cameras are being carried around with light coming through the lens directly onto the shutter.
Marty
p.giannakis
Pan Giannakis
Dual shutter curtains are nothing new. They are used to ensure that no light leaks through shutter blades in high speeds due to vibrations. Nikons F4 and F5 (possibly F6 too) has them.
zuiko85
Mentor
Does the Leica metal shutter also have a second set of blades?
Freakscene
Obscure member
It depends which Leica metal shutter you mean. The Leica shutter in the digital M cameras is light tight. Cosina obviously thought that outsourcing shutter construction was advantageous when they designed the Bessas. Constructing shutters is not exactly simple, and while Copal exists and builds shutters the approach Cosina took for the Bessas makes sense.
Marty
Ko.Fe.
Lenses 35/21 Gears 46/20
Bingo ! ! !
agentlossing
Well-known
Neat! All the more reason CV shutters sound so much like SLR shutters.
santino
FSU gear head
I wonder about the Bessaflex... does it have despite the mirror a double shutter too?
Freakscene
Obscure member
santino
FSU gear head
That makes sense. The M6 prototype had the shutter of the R series. They dropped the whole concept because it wasn‘t light tight.
charjohncarter
Mentor
Thanks Mary and Pan. Very clear with your explanation.
mpaniagua
Newby photographer
Thanks guy. Very educational and was curioius on the Bessa's double shutter/blades for a while. They are prettty interesting machines.
Marcelo
Marcelo
TenEleven
Well-known
Seconding that this is very cool and sates a long-standing curiosity of mine.
Is there any chance we could see a shot that shows how far the two shutters are apart from each other? It's a bit hard to visualize that with the current pictures.
Either way, many thanks!
Is there any chance we could see a shot that shows how far the two shutters are apart from each other? It's a bit hard to visualize that with the current pictures.
Either way, many thanks!
monopix
Cam repairer
The camera is already back together so I can't take another shot but the two shutters are right against each other. If you look at the first picture and see the two holes in the chassis right above the shutter. Then look at the second picture at the two threaded holes above the other shutter. Well they mate together so that should give you an idea of how close they are.