In addition to the usual blown up prints of his most famous images, they had contact sheets from his film rolls, and they really showed how incredibly skilled he was.
From looking at the contact sheets, and comparing with the blown-up images, you could see that 95% of his shots were perfectly composed, well exposed, in focus, and there were almost no wasted shots at all—none of this "take multiple exposures and choose the best one" business, he just got it right the first time and moved on.
While being shot at.
I liked his work before seeing that exhibition, but I was in awe after it...
[and of course while the equipment of the time (from the contact sheets, you could see it was 35mm film) wasn't all that bad, it was a bit primitive compared to what we have now....]