Hi, I had a Canon 5D and 20-70mm L-series lens, which is similar size/weight to your 50D. I initially planned to put it in an Ortlieb bar bag, but it filled the bag, would not have been protected in a crash, and left no room for anything else. In the end, I put it in it's small Lowepro case at the top of my pannier. When I stopped for cafe/shop, I took my bar bag and camera. Another factor is that the extra weight in the bar bag affects steering, and can make the bar bag bounce around, which is quite disconcerting.