I just returned from a week in Colorado visiting family. I spent a couple of days hiking in the mountains above Denver, and encountered highly changeable weather conditions and lighting challenges -- typical of this time of the year in the high country.
The overcast but very bright skies and dark forests made use of graduated ND filters almost a necessity to reduce the dynamic range of the images. I also tested a new 105mm Singh-Ray Color Combo Polarizer that I mounted on my Lee 100 filter holder. Was pleased with the ability of that filter to boost browns and greens, as can be seen in some of the results below.