Runners dress for fit, form, and function. Fashion is not a priority, nor is hair or make-up. You get what you get as the photographer. If it rains on the runner, it rains on you. If it is a hot and sunny day, so it is with you. The action does not stop for any image with the exception of pre-race and post-race start/finish pictures. Borderline chaos is assured for the photographer invited to shoot with a runner.
