Curious about the Aperature Ring

Does the aperature ring on the RX and other AE contaxes directly control the diaphram or does it mearly tell the camera where to set the aperature and let the camera's electronics and motors set the aperature on exposure and preview?
 
D

dja

>>Does the aperature ring on the RX and other AE contaxes directly control the diaphram or does it mearly tell the camera where to set the aperature and let the camera's electronics and motors set the aperature on exposure and preview?<<

Shawn, I'm easy to confuse. You are talking about the aperture ring on the *lenses* right?

There is a small tab inside the mount to register the aperture setting on the lens. Looking at the mount it's at the one o'clock position.

The camera holds the aperture wide open to allow maximum image brightness for focusing. When the picture is taken, the camera allows the lens to close down to the user selected aperture. It's the same thing that happens when using the DOF preview. It's mechanical.

David
 
Dave- I am sorry I was not more clear. Yes, i meant on the lense, what other ring is there??

On manual exposure cameras the aperature ring directly controls the diaphram, a trigger simply activates it.

On AE systems, is the ring mearly an electronic switch that has no mechanical coupling to the diaphram but rather sends electrical information to the camera telling it where to stop down?
 
D

dja

>>On manual exposure cameras the aperature ring directly controls the diaphram, a trigger simply activates it.

On AE systems, is the ring mearly an electronic switch that has no mechanical coupling to the diaphram but rather sends electrical information to the camera telling it where to stop down?<<


The only thing close to what you may be asking is related to shutter priority (or program) mode. In tv mode, the aperture setting is determined by the camera. The lens is set to it's smallest aperture and at the moment of exposure, the camera moves the lens diaphram to the appropriate aperture. Or, more accurately, the camera relaxes force against the diaphram spring which closes down the aperture.

Electronics make the decision, but springs and levers make the exposure.

Dave
 
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