The MR4 meter is a reflected light meter that couples to the shutter speeed dial of many M cameras. It has a sensitivity range of EV +2 to +18. That means with a film of ISO 100 It will give you readings from F1.4 @ 2 seconds to F16 @ 1/1,000th of a second. That covers pretty much of what most people need in many circumstances. Once you attach it to the M3 it will read an angle of view more or less equal to the angle of view of a 90mm lens. This is the angle of view shown by the frame lines either when you insert a 90mm lens into the camera & attach it or when you push the lever under the large, clear viewfinder window in the front of the camera inward in the direction of the center of the camera. Until that lever stops moving. Regardless of the lens mounted. Unless the lens has permanently attached “goggles”. If the lens on the camera has permanently attached “goggles”: Push that same lever outwards until it stops & use the 135mm frame. Sounds silly but it works correctly. Replacement Wein 1.35 volt zinc-air “button” batteries are available. Just check in any camera store or find them on the net……..

Source: leicaphilia.com

Leica MR4 meter Leicaphilia