The more I learn about photography the more difficult I find it

Lighting used to be as simple/difficult as placing the light, getting the exposure right and away you go. Now, as I try to experiment a little more, using hair lights or even just a single light but positioning the model and light for required softness and fall off, it's all a little more technical.

And then the model moves Some models are very light aware, but I find most aren't. I love when a model is free to move and pose and the shoot is quite fluid. But with this fluidity comes at the expense of lighting.

So how do other photographers cope with this? Build in enough margin into their setups to allow for a great deal of movement? Restrict the model? Go for a technical setup, let the model do his/her thing and worry about afterwards in processing?

An interesting thread you've started here Ciaran and it's something I've grappled with myself, but the more I learn about lighting the less I worry about a model moving. That's probably the exact opposite from your own experience, but then again I suppose I work more with available light and less so with studio based lighting but there are a few things I have discovered in recent times (these may not be anything new to anyone, but they helped me).

I used to think that a hair light had to come from a snoot or gridded spot, which meant of course that the model had to be rigidly stuck to one place. But I now realise that even the humble umbrella may be used as a hairlight, giving a much larger degree of freedom of movement.

Another issue I had was dealing with light fall off or changes in exposure if a model moved further or closer to the key light. Again, the solution was so simple I never really thought of it. Using a more powerful light source from further away means that relative effects of the inverse square law are less noticeable (hope that makes sense). Of course, this may mean having to use a larger light source to counteract the effect of having the source further away from the subject.

Of course the other thing to consider is that some models can be directed very well, and will adopt very precise positioning according to your instructions. When you have such a model you can be far more precise with your lighting and not worry about it going wrong because the model moved. But like you, I also love when a model is free to move and pose as she wishes making the shoot quite fluid. I don't agree that this has to come at the expense of lighting. Sure, it may limit your lighting options, but you can't have your bread buttered on both sides.

I guess I should have specified that I am talking specifically about studio lighting, rather than ambient/available light.

But the issue with using a larger point source (i.e. softbox, umbrella) is that the spread of light is harder (impossible?) to control. You do get a much larger degree of freedom in movement, but you'll also inevitably end up with the hair light spilling on to shoulders, arms, cheeks etc.

Point taken again, but it's the drop off that gives you the drama! If you move the key light further away, there's less drop off across the model, with the light becoming flatter and less drama.

Here's a shot where I used a main light (close for drama/softness) as well as a hair light

I do agree, but I worked with a model before and she moved SOO much from pose to pose, moving easily at least double the distance from the main light than where initially placed, then sitting down on the ground, then back up again. Changing the light each time would have been impossible and would have destroyed all fluidity. Nailing her to the initial spot would have had the same effect So I chose to let the shoot go and fix later (shots turned out to be just OK... so I do take your point)

i put down a bit of blue tack where i want the model to stand and explain to them why i want them to keep that position. I then try and keep an eye that they are maintaining this and correct it if not.

My light sources are getting tighter and tighter.. if the bloody striplights I ordered 6 weeks ago would actually arrive, I'd probably have more to say about it.. I was also talking to Simon Young about it recently and he's actually directing me towards tighter lighting for better control. 

Tighter light just needs tighter posing.... I don't really see any way around it. 

More distance will provide more even coverage at the expense of transition.. We all know this. 

Thorsten talks of compromise, but in reality to achieve the technical control we require to achieve our artistic goals, we can't compromise. It takes holding fast to get where we want to go. 

Maybe this needs to be addressed when booking the model. When you're looking lots of looks and fluid posing, then book a suitable model. When you need tighter, controlled looks, then find a different model... 

Actually I think you're probably right when you say this. Your lighting goal vs the models ability to pose and be light aware have to be matched. Thorstens idea of a lighting 101 for models is an interesting one, but I fear also a pointless one. The turn over of models is so high, you'd never be able to even come close to addressing the market. And that assumes there'd be interest in the first place!

While it may not always be possible to have a lighting assistant, getting one to handle a snoot may get you that extra degree of control, which might allow for balance in relating fluid movement to light control.

Thats actually a superb tip. I've found having someone along to assist you on a shoot an invaluable asset. Not just for lighting, but it's certainly beneficial in that case.