Is Peaking 100% good enough
 

I shot a ballet in a theatre where the tech crew went through the motions but were not very good at keeping the lighting reasonable consistent and balanced so that I had spot mtr/focus engaged the whole time constantly touching the screen to adjust but found that process a little sketchy.
Is focus peaking good enough when shooting 4k or what other focus/exposure techniques could be used in a theatre setting please

Re: Is Peaking 100% good enough
 

In my opinion focusing manually is always best for motion imaging. To this day, despite all the technology out there, motion picture films still focus cameras manually. However, they facilitate a camera assistant or "focus puller" who takes measurements and marks the lens correspondingly prior to the shot. And the shots are typically ones where the subjects hit preset marks, or close to preset marks.

When a camera operator pulls focus it is typically done by eye. That is where the peaking function comes in. Using peaking to assist focusing by eye is about the best option available. Lenses with purely mechanical focus that react rapidly and consistently make for your best shot at focusing by eye.

Peaking is not always accurate. That is, peaking may indicate that something is in focus but it isn't actually in critical focus.

From your description of your situation, there wasn't much you could do. Possibly you could have instructed the Lighting crew to give you as much light as possible so as to increase your F-stop ( smaller iris opening ) and thus increase your depth of focus at any given focal length. Practicing the focus pulls on a rehearsal of the event, on the same stage and from the same camera position, would have been of help. As you no doubt found out ( and likely already knew ), the more you zoomed in the more difficult it was to maintain focus. Thus the saying in tv sports shooting of "when in doubt, pull out" ( or, at least cease zooming in. )

I have never used auto-focus on any camera so I can't help you with any techniques or tricks regarding auto focus. For most of my career I was using zooms that were fully manual and did not have any auto-focus even had I sunk to using it. ( j/k about the "sunk" part! ). I have recently experienced first hand how the focus action on some lenses is so crappy that using auto-focus full time or intermittently is actually better than attempting to focus manually. I was spoiled on the +$30k zooms and arrogantly thought that people who did not focus manually just lacked talent. I can now understand why many use auto focus, particularly on lenses designed for still photography. No focus end stops? No direct response? Short focus throw?? Not par focal??? Wow. What a nightmare. Yeah, switch that crap glass to auto focus and then babysit the AF.

Re: Is Peaking 100% good enough
 

I find that on the HD versions of these cameras that the peaking has a WIDE latitude, meaning you can rack focus in front of and past your sharp focus point, and the peaking "smear" will still show the same effect.

Paul