Road to Yellowstone 2007. Equipment Used: Canon 30D, Tamron SP-AF 17-50mm f/2.8 with Polarizer, Canon EF 70-200mm f/4L USM with Moose 81A Polarizer, also Cokin P-Series filter set; P028 warm, P120 GND, P121 GND were used together, interchangeably, with either lens. Dynatran AT-858BL Tripod with ATH-918 grip action ball head.