Although I’ve never liked it when the camera’s on a tripod, focus peaking has great potential with the camera handheld. That’s because it offers the chance to focus without zooming in and losing the context of he whole image, a. Also, if it’s sensitive enough, you should be able to focus at the taking aperture, speeding things along a lot. However, with the Zeiss 35mm f/2 Biogon on the a7S, that promise goes pretty much unfulfilled.
The first reason is that, even when you turn it down to minimum, the peaking effect is too strong, filling practically the whole screen with red lines if the focus is in the same county as what’s correct. Sony could fix that at the risk of making peaking too weak for flat scenes with long lenses, but I have a better idea.
When a non-AF lens that doesn’t allow the camera body to control the aperture is mounted, that dial currently becomes useless; you can turn it all you want and nothing will happen. Why not reprogram the firmware so that, under those conditions, that knob controls the sensitivity of focus peaking in, say, 20 steps. You could twiddle it until you find just the right setting for the lens you’re using the the scene you’re photographing.
Sony, take this idea and run with it. I want no compensation or credit should you decide to use it.