Leica was serious when they took pride in the M4 as a no-frills, no electronics “think camera” for pro photographers.

Leica cameras have come to mean many things to photographers then and now, but one model, in particular, was dubbed by the company itself as the camera for the thinking photographer. In a vintage print ad, the Leica M4 was marketed as the camera for pros who want to take full control of their camera settings and put their full creativity to work. None of those electronic functions like auto exposure and autofocus — just pure photography skills at work.
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https://www.thephoblographer.com/2020/04/25/the-leica-m4-a-camera-for-the-thinking-photographer/