Some interesting points made in this blog: http://blog.oilpaintersofamerica.com/2012/08/paint-from-life-or-photos/
http://www.artiscreation.com/red.html#PR264 image above from the extremely useful Dick Blick website to which this pigment database links.
Many thanks to Golden for this article showing the results of tests of various "sizes" (ways of sealing canvas) including RSG. Image from same source. http://www.justpaint.org/preparing-a-canvas-for-oil-painting/