Indoor photography is the bain of all equine photographers - I have given up completely - and if the show is indoors I work the collecting area (outside) and take the champions outside for their official sponsorship pictures. I ask the anouncer and the stewards to tell the winners they have to come outside for pictures.
Its funny but once they have been given a ribbon they are much more agreeable to pose and smile - so there are candid shots and winning shots from my indoor shows. both sell quite well
