A few years ago, my father in law and I attended the Longford "flying mile" vintage car event. The event is a celebration of the Formula 1 race that Longford used to host back in the 60's.
At the time I was shooting with Canon crop frame (450D) cameras after doing without full frame for a long while. Temptation got the better of me again and I borrowed, with the intention of buying, a 5D mk2 for the event.
One of the images below was taken with the full frame, two with the 450D and one with my EPL3 Olympus. The Olympus was sporting a kit lens, the Canons shared a 35(55)L and 135(210)L combination. All of the shots were taken in the open or under a white tent cover.
After the event, I printed a composite poster of the images and often used it as an example of the difference between full and crop frame. It was good for showing that fewer pixels on a smaller sensor could fool anyone (our visiting Nikon rep for example) with similar processing up to pretty reasonable sizes.
The answer to the little riddle? The Olympus image is the most obvious- the helmeted figure. It's sharp and very clear, but looks 'thinner" than the Canon ones. Part of this is due to the brands' look, but much of the difference is in the Canon-centric processing style used at the time.
The red and black bonnet is the full frame image, the others are the 450D, but really you can only tell when 40" prints are made.
Yes I bought the 5D mk2, but the Olympus "rot" had set in, just waiting for the right camera and a few more lenses.