Why do 35mm SLR cameras need batteries?
In the OFF position, the camera works only if the film advance lever has been cocked. The idea was that if you saw a sudden opportunity for a shot and pressed the shutter the camera would take the best exposure it could with the aperture available. It’s a much better system than on modern digicams where you have to wait ages for the camera to turn on or even wake up from sleep mode. In the OM10’s off mode, the viewfinder and lightmeter were unpowered, but at the moment of exposure the camera’s off the film metering would briefly power up. In the off position you will not get the really long off the film exposures which the camera is capable of at night. The batteries are therefore necessary to power the lightmeter even if you didn’t know that it powered up, but the batteries also power the shutter. The film advance lever winds back the shutter curtains, but their release is via electromagnetic switches which need battery power. The battery also powers the self-timer. if the batteries r
