Of course 35mm could be blown up directly. That's what blazingly hot mural enlargers were for; and there was even a franchise in a number of cities with a tower outside the bldg which looked like a grain
silo, and was basically a huge vertical enlarger. Pro labs used big horizontal enlargers. But the correct
way to do it was to enlarge your small image onto an 8x1 to 12x16 interneg or dupe chrome first, depending. Nowadays I could just walk into the CBS Outdoor Adv Co down the street and they'd scan
something and put it on either a traditional or digital billboard. That kind of thing is disgusting enough
cluttering our outdoor space. I don't know why anyone would want it indoors too.