I am shooting a western however, I am doing so in Scotland - it is very green here. My plan WAS to have the actors paths that they walk be sand and then use green screen behind them in order to make the rest of the ground dry sand.
I am now wondering if it is possible to key out grass (with the exception of where the actors walk) and use AE to turn it to sand. I however, am not sure if this is unrealistic.?
Any advice would be very much appreciated - I am relatively new to After Effects.
You wouldn't key anthing. You'd simply completely replace it and that can be done most efficiently by applying some rough animated masks around the sand areas.
Grass is not colored uniformly enough to allow good keying in most cases. I see that you're trying to avoid using the green screen, but you're probably going to have to. You could give it a quick test though and see for yourself.
How did you end up solving this issue? Keying? Masks? Please let us know. Sounds like an interesting project.