Marc - I think you need to read further in that definition and page. My understanding of key lighting is that it is derived from the 3 light system used in the studio where the key light was set at a 15-45 degree angle from the camera as the direct light source and then the other two lights in the system were the fill light and the backlight. The key light if used alone creates deep shadows. What we are looking for in the theme is those images that have become somewhat popular in nature photography where there's a strong direct light source illuminating a part of the animal and then the bg is darker, like Gabriela's image here:
http://www.birdphotographers.net/for...ll-Try-To-quot
We can have backlit images as the theme another month.
Thanks,
Rachel