The performance of the cast is on the short-list of the most important things in my films. The cast is who the audience connects to, they have to feel real.
Agreed. Great lighting, cinematography and sound are all meaningless if the audience is pulled out of the scene/film by lousy acting and poor acting is probably the most easily identifiable way of loosing the audience. That's why film reviewers and even the public virtually always mention the acting but much less commonly the sound or lighting. As filmmakers though, we need a deeper understanding, we need to look beyond just the most obvious and understand that the less obvious does not mean less important. We can all make comments/judgements about the architecture of buildings but not so much about the field of structural engineering because the architecture is obvious and the structural engineering much less so. We take for granted that the structural engineering is competent and only mention it on those rare occasions when it's deliberately been made particularly obvious or when it's not competent. Of course, just because we expect and take structural engineering competency for granted doesn't mean that it's easy to achieve, of less importance and taken for granted by those who actually make buildings! In other words, good architectural design requires good structural engineering to translate that design into a good building, without good structural engineering it doesn't matter how great the architecture, it will never be a good building.
So it is with filmmaking. It doesn't matter how good a performance is achieved on set unless it can be translated into a good film. This, IMHO, is the biggest difference between hobbyists/amateurs and professionals: For most hobbyists/amateurs, production is the most famous and enjoyable part of filmmaking and pre-production exists simply to put all the logistics/organisation in place so that production can occur with as few problems/distractions as possible. For the professional, the point/target of pre-production is not production but post-production! Although of course, production is a vitally important step along the way and still needs to occur with as few problems as possible. This difference is huge because once the hobbyist/amateur has wrapped, they've now got a hard drive full of footage which they've somehow got to edit together to create an intriguing, involving "shape" while constrained by both the need to make the story coherent and the pace/shape of the footage they've captured. While luck may lend a hand in some places, in others it won't. The result is second guessing, indecision and re-cuts, in the hope of finding that perfect editing solution (which probably doesn't even exist), finally ending when the filmmaker eventually runs out of resources (time, money and/or the will to live!), and that's if the filmmaker is even aware of severe structural weaknesses in the first place! The professional filmmaker on the other hand has reduced this near impossible task to merely a difficult task because the "footage they've captured" has been specifically designed with the right pace/shape (or the opportunities to create it) as the primary goal from the outset!
Damn, I got some stuff to think about.
Yep, if you want to do something which doesn't require a lot of "stuff to think about", the role of film director would be near the bottom of that list! Rather than think about it that way though, think about it the other way around. If you don't think about it in pre, you're going to have to think about it in post or ignore it and just live with the consequences. At least thinking about it in pre presents the opportunity of doing something about it, of making changes to any prior decisions/choices to solve or at least minimise any issues. Come post there maybe less to think about but only because you're largely stuck with the decisions/choices you've already made!
There's gotta be a happy-middle ...
Often yes but not always. Sometimes there's no choice but to sacrifice something during production. Working this out in pre, before you get to it, is still preferable though. For example, take a scene/shot where it's just not practical or realistically possible to get usable prod sound. Figuring this out in pre means you can mitigate it better and still maximise your resources. If you know you're going to need ADR in pre, arrange your shooting schedule so you don't need to pay the PSM that day, put that money into the audio post budget to get decent ADR instead! Also, pare the dialogue for that shot/scene down to it's bare minimum while still prioritising shape (take a day or two to think about how, you've no cast and crew hanging around for your on the spot solution!) and make sure your actor enunciates clearly so lip sync in post will be easy or, design the shot/lighting/angle so that precise lip sync isn't even going to be necessary!
...maybe I select some scenes to be rehearsed and blocked well in-advance, based on production needs, while the ones that are easier to shoot can be rehearsed just before shooting.
Now you're thinking smart, rather than just "easy"! Most hobbyists/amateurs are thinking in terms of "easy", what gets them to the production phase most easily, what makes it easiest to get to the end. For this reason, they usually think in large, generalised terms, with the fewest number of rules which they apply in a blanket fashion. For example, on set acting performance or cinematography (or whatever) being a priority and therefore always being a priority, for every shot, for every scene, regardless of how that will affect the audiences' perception of the film when all those shots/scenes are edited together. There is no one right or wrong way, there are a lot of different ways each of which are right or wrong depending on the needs of each shot/scene and more importantly still; the needs of how those scene are all going to be perceived by an audience when strung together! Yes, it's a lot more work in pre to figure out which "way" is best for each scene and then budgeting/organising all those "ways". It's certainly a hell of a lot easier to just pick a "way" and apply it to every scene! With little/no budget, completing a feature length film is very difficult, so it's entirely logical to make that very difficult task as simple and easy as possible. However, you've already achieved that, you're now looking at an even bigger leap in difficulty, not just completing a film, not even completing a film which is watchable but one which is so watchable people will pay to watch it! Doing the same as you did before, even doing the same but better is not going to get you where you want. Your competition is no longer other hobbyists trying to achieve a very difficult task, your competition is now the very best aspiring amateurs and the professionals and even making an excellent hobbyist film is not going to cut it! You've got to do it differently, play by different rules, rules which are dominated by the structure, quality and therefore audience perception of the end result, rather than making the process as simple/easy as practical. I'm not being negative here but the opposite; yes, you've got to be both much smarter and work much harder but the only thing which can stop you being both is you (!) and the pay-off is that those virtually impossible odds of success become way less impossible!
The only wording in the quote above I would change is; "based on production needs" which should be changed to "based on post-production needs"!
G