Ian already answered your question accurately, but I'd like to punctuate the rest of his comments. I chuckle at the concept of "amateur versus professional" cameras because during the small part of my career (about 8 years) that involved using a camera I used amateur cameras exclusively, yet at the same time I did all of my personal amateur photography using a professional camera. There was a difference, though. The cameras used professionally were overhauled at least annually and were replaced after about 3 years. I'm thinking that if we were using professional cameras in the same conditions they may have only needed overhaul every 18 months and may not have had to be replaced.

And speaking of National Geographic... we ended up shooting side-by-side with a NatGeo photographer. This was in a very dangerous and difficult industrial setting He had gear, and more gear, and then more. We were shooting amateur equipment and using a minimalist approach. We had an opportunity to share images after the session and he liked ours better. His looked like studio shots and ours looked like "real life". It was an interesting discussion to say the least.