I read an article about the use of a view finder when creating art out side. It helps you focus in on a composition. Being cheap I decided to make my own from left over cardboard. I love it. I use it too for still lifes. It helps me arrange a set up. To take it a step further, on difficult set ups like the one I am working on now, I tape some pieces of thread across it to make a grid. I then make the same grid on the painting surface and it make my life a lot easier.
I got the idea from Van Gogh who had a carpenter make a large frame on a tripod. In the frame he had a series of wires to make a grid.
Here is a picture of my view finder and my improved start for my painting.