Professional Photographer and Border Crossings

I'm sure that this came up on the 'Border Security' show, but I cannot remember the outcome. I don't know how they would differentiate between an enthusiastic amateur with lots of equipment and a professional photographer. I think you would only have a problem if you admitted it at the border. "I work for Sports Illustrated and I am coming to Canada to film the Surfing Championship at Tofino" I am sure in that case you would need a work permit.