Just so you know 150 dpi is much less than 300 dpi, not half. What you have to remember is its really 150 x 150 dpi per square inch which is 22,500 dots, whereas 300 x 300 dpi is 90,000 dots, which is four times the resolution. 600 x 600 dpi is 360,000 dots or four times 300 dpi resolution. The difference in quality between these three commonly printed resolutions is vast, really.

GP