Single Button Adjusts Camera for Making Any Snapshot (Apr, 1940)
If you move something to various positions I’m pretty sure it shouldn’t be called a “button”.
Single Button Adjusts Camera for Making Any Snapshot
As A convenient time-saver for snapshooters, a new camera is equipped with a lens diaphragm that is coupled to the setting mechanism of the shutter so that only one adjustment is necessary before taking a picture. For example, when taking a picture on a cloudy day, a button on the front of the camera is moved to a point marked “cloudy.” The operation determines both the shutter speed and the size of the diaphragm opening so that when the scene is snapped the film will be given just the right amount of light for a good picture.