I am planning to get a circular polarizer for automotive photography. I use my Canon 15-85mm and Sigma 30mm f/1.4. The thing is that I do not know which lens to get a polarizer for. I do not have funds to get it for both. I like how the 30mm has great bokeh. But it seems like it would be more versatile for me to get it for the 15-85, yet it does not produce as nice of a background blur. What do you guys think?