At a recent conference in which I presented some data from immunoblot experiments I was asked a question for which I didn't have a good answer. I was asked how did I ensure that the film that I was using to develop the westerns was showing bands in the linear range of the film? The person asking the question thought that some of the bands shown on the westerns appeared to be saturated. All I could say was that we exposed the film long enough to see a band in our control sample. I couldn't really answer the question. Can anyone help me with this? How can you ensure that you are in the linear range of the film when you are exposing a western?