Attached Link: http://www.retouchpro.com/tutorials/lum-mask-sepia.html

>coming up with a whole set of toning parameters I generally use a method similar to that given in this link. It's the best procedure I've found, but even it has some shortcomings. [You can use other colors than sepia; a nice purple works well to simulate selenium.] Still, this method is not perfect. I've yet to simulate a platinum print, for example. If you come up with some good techniques, please do a tutorial for Michelle and Star.