Have a plan - or not?

I recently arranged a fashion collaboration shoot - this is something we do once a month as a creative exercise. Everyone who gets involved commits 100% and we have lots of fun with the opportunity to try different things. On this particular shoot I worked out that we would have about two hours at the location and knew we were going for three different looks. I decided that I would go for three different lighting scenarios, dark, back-lit and blue.

 

On the day I worked through the scenarios and got some ok results similar to my visualisations. Having gone with a plan and completed it I should be happy but I am not! I think working to the plan actually stopped my creativity.

I suspect that if I had just turned up and gone with my instinct I would have got better results but obviously I can't prove it either way. At the start of the session there were some great natural light opportunities that I missed. The danger of not planning is that potentially you could dry up and not come up with any ideas but does over planning sap creativity?