So here I am sitting on a small boat at dusk where the Sea of Cortez meets the Pacific photographing whales. I am using one of those "antique film rangefinders" that are fairly common around here, an Leica M with a 35mm lens. You don't know were or when the whale is going to pop up or how far or close to the boat. I set the lens on infinity so after 25 feet I should be in focus. Set the f/stop based upon the ocean and available light, somewhere around f2.8 & 2.0 & wait. Now the others with the DSLRs on automatic would point the camera wait for it to focus & read the light & set the aperture & f/stop accordingly. After each shot they turned the camera off to see if they captured the image, which took time to come up on the screen. In the interim if the whale changed its mind and came up early they were stuck looking at the screen. That old M managed 2 rolls of film.