The reindeer (Rangifer tarandus), also known as the caribou in North America, is a species of deer with circumpolar distribution, native to Arctic, subarctic, tundra, boreal, and mountainous regions of range of caribou extends from Alaska through the Yukon, the Northwest Territories and Nunavut into the boreal forest and south through the Canadian Rockies. The barren-ground caribou, Porcupine caribou, and Peary caribou live in the tundra, while the boreal woodland caribou prefer the boreal forest. The Porcupine caribou and the barren-ground caribou form large herds and undertake lengthy seasonal migrations from birthing grounds to summer and winter feeding grounds in the tundra and taiga. The migrations of Porcupine caribou herds are among the longest of any mammal. Barren-ground caribou are also found in Kitaa in Greenland, but the larger herds are in Alaska, the Northwest Territories, and Nunavut.
Chroma key compositing, or chroma keying, is a special effects / post-production technique for compositing (layering) two images or video streams together based on color hues (chroma range). The technique has been used heavily in many fields to remove a background from the subject of a photo or video – particularly the newscasting, motion picture and videogame industries. A color range in the foreground footage is made transparent, allowing separately filmed background footage or a static image to be inserted into the scene. The chroma keying technique is commonly used in video production and post-production. This technique is also referred to as color keying, colour-separation overlay (CSO; primarily by the BBC), or by various terms for specific color-related variants such as green screen, and blue screen – chroma keying can be done with backgrounds of any color that are uniform and distinct, but green and blue backgrounds are more commonly used because they differ most distinctly in hue from most human skin colors. No part of the subject being filmed or photographed may duplicate the color used as the backing.