I quite often shoot with large format cameras, even though they look old fashion, there are still quite a few companies that make these cameras, I used to manufacture the glass screens that go in the back of them so you can focus your image on the viewing screen, when it comes to photography, bigger is always better, I suspect, he was probably shooting a 8inch x 10inch camera, that means each negative is 8in x 10 in in size, and came be duplicated in magazines very easy, and also can be blown up to very large sizes, the largest cameras I ever shot are 16inches x 20inches and 20 x 24 inches, that was the size of my negative or my slide, depending on the type of film I was shooting that day.
The little tube he was looking through would be a micro focusing loupe, to anaylize the critical focus on the viewing screen and he was also using an exposure meter (the pistol) and making adjustments to his exposure and f/stop on his lens, I would suspect from what you described, he was shooting at f/64 or higher, which require long exposures to get the proper exposure on the film.
My largest camera now is a 4x5 in, I use it a lot for shooting product advertising panels for companies, normally with provia 100 slide file, then they are drum scanned into digital format for layouts in magazines.
But the large format business is still quite a good market, as just a note, in the 3 years I made camera viewing screens, I shipped over 50,000 screens all over the world, it was quite a business.
When you run into a dedicated large format shooting, often times, they are very secretive of their techniques, in addition, the film they are shooting is very expensive, a box of 8x10 provia film runs well over $100 for ten shots, so if you screw it up because of a distraction, it can be very expensive, if he was shooting an 11x14 in camera, then your talking over $250.00 for 10 shots, 16 x 20 film is over $800.00 for 10 shots!, so they really are not trying to be rude, but they do hold to their techniques as highly guarded secrets as well as keeping their mind in the game and waiting or exactly the right moment to push the shutter button..
And its no bother, I always enjoy talking about photography of any type..one thing I will add, those large cameras, if they are new, or even restored old ones, with lenses and shutters can run in the tens of thousands of dollars, just my little 4x5 would with lenses and shutters that I have would run over $3000.00 to replace at today's prices..but a good 11x14 camera will run quite a bit more than the most expensive pro digital cameras..