Focus peaking is turned off by the half-press. Just shoot. Legacy glass designed for film cameras can be a disaster depending upon the design of the lens. I have two Canon Serenars of considerable age, both with flat rear elements. Film is matte, but sensors are shiny, so the light bounces back and forth between them, destroying contrast.
Many very fast vintage lenses are notoriously soft wide open. They were designed to help focus SLR film cameras in low-light and could be used wide-open in an emergency but at considerable cost in sharpness. Working for a morning paper, much of my work was in available darkness. The classic f/1.2 58mm Nikkor helped a lot, but I tried to keep it at a minimum of f/2.0-2.8 for the actual exposure. At the time, Nikon made the f/1.2 Noct-Nikkor, which was optimized for widest aperture shooting, but at the price I could not convince my boss that it would provide enough return on investment.
Dude reacted to Larry Bolch in focus help needed for X-E1 with manual vintage glass