Gerry M
Gerry
Do all m4/3 adapters for manual focus lens (OM to G1 body) require stop down metering?
JoeV
Thin Air, Bright Sun
All manual focus lens adapters for m4/3 should permit the lens aperture to always be "stopped down."
The reason for this is that these old lenses, when attached to their intended manual SLR camera bodies, would have a mechanical linkage from the camera, actuated when the shutter was tripped, that stopped down the aperture just before the shutter opens.
Micro-4/3 camera bodies don't have such a mechanical linkage, so the lens adapter ring has to permit the lens to always be "stopped down," meaning that as you turn the aperture ring on the lens you can immediately see the lens aperture change. This is also an advantage, as you can preview your DOF effects without losing image brightness through a restricted aperture.
When attached to a micro-4/3 body via an adapter ring, metering takes place through whatever aperture the lens is already stopped down to. You have to set the camera body to aperture priority, and the EVF/LCD will "gain up" (amplifiy the signal through the stopped-down aperture) to keep the live view image constant brightness. This is the biggest difference between using these lenses on micro-4/3 bodies via adapter rings and using them on their intended manual SLR body, where the manual DOF preview button would stop down the lens but the image would consequently get dim because of the loss of light through the small lens aperture.
~Joe
The reason for this is that these old lenses, when attached to their intended manual SLR camera bodies, would have a mechanical linkage from the camera, actuated when the shutter was tripped, that stopped down the aperture just before the shutter opens.
Micro-4/3 camera bodies don't have such a mechanical linkage, so the lens adapter ring has to permit the lens to always be "stopped down," meaning that as you turn the aperture ring on the lens you can immediately see the lens aperture change. This is also an advantage, as you can preview your DOF effects without losing image brightness through a restricted aperture.
When attached to a micro-4/3 body via an adapter ring, metering takes place through whatever aperture the lens is already stopped down to. You have to set the camera body to aperture priority, and the EVF/LCD will "gain up" (amplifiy the signal through the stopped-down aperture) to keep the live view image constant brightness. This is the biggest difference between using these lenses on micro-4/3 bodies via adapter rings and using them on their intended manual SLR body, where the manual DOF preview button would stop down the lens but the image would consequently get dim because of the loss of light through the small lens aperture.
~Joe
Gerry M
Gerry
JoeV,
Thanks for the explanation. It helps greatly.
Thanks for the explanation. It helps greatly.