The bar is lit exactly as it is lit throughout the film. If it seems too bright, consider this: if YOU were Mama Chunk, and you had a bar full of native AND foreign riff-raff, several pimps, AND a bunch of rowdy, drunk sailors, would YOU want a dimly-lit environment in which a scenario such as this were played out? I think not.

That may be true but they were more than likely thinking about the bottom line. In 1966 Studios were not giving up a lot of money for pictures. This one was already behind schedule so a sound stage was the best they could more than likely do. I could be wrong but knowing how the "heads" thoughtbottom line was probably the main culprit.