A more complete version of that photo appears on page 13 of the MagicImage Filmscript book.  Here is the best I could scan it without damaging the binding:



The accompanying text reads:

Noble Johnson peers through the cab window while David Manners and Zita Johann sit in the mock-up car.  Boris Karloff and an extra stand at the car door.  To the right are Director Karl Freund (seated), behind him William Pogany the set designer and artist, Mis Johann's driver Sasha, Carl Laemmle Jr., the script girl and crew.  To the far left you will see the rear projection process camera/projector and its operators.