How did analyzing film posters help me?

Whilst trying to design my film poster I found it incredibly difficult to visualize what it would look like. So in order to gain an idea of what type of structure I would be looking into I analyzed a few film posters. Whilst doing this I was able to identify various aspects that they had in common and which things differed from genre to genre. So now I had a list of the different conventions I was able to decide which conventions I wanted to follow and which ones if any I wanted to challenge. I wanted to have my poster in landscape format with a single image of the main characters from my film. I wanted to take a picture that would inform the audience of which characters are in which role in the film. At first I wanted to use afilm screen shot but I then decided it would be better if I was to go out and take a suitable picture. I drew up a design of the poster just to make it easier for me when I was putting it together on photoshop.