Commercial photography was and is a subset of photographic specialties practiced by professional photographers. The product is illumined by several lamps. These can be continuous or electronic flash. Lighting products like machines and merchandise is an acquired skill, lots and lots of practice. In that era, likely 4 X 5 inch sheet film was used. however, roll film works also. After the picture was taken, the film was developed and printed. Careful attention was paid when printing on photo paper to get an optimum print. Optimum means a print with the proper contrast for what follows. The finished photographic print was sent to the printer. At the printers, they used a razor knife, like a scalpel, and cut around the image. This cut-out was pasted to a white paper background. This past-up, with other images was taken to a process camera. This is a special camera that features a finely lined screen etched on glass that hovers a millimeter or so above the copy film. An alternative was to use a special copy film that has a built-in screen. The purpose of the screen is to break up the continuous tones of the image into a halftone. This process makes a halftone negative image that consist of dots. The size and spacing of each dot is proportional to the various shades of gray on the original print. The halftone negative is then exposed onto a zinc plate coated with a special photographic emulsion. When developed the emulsion on the plate is present or absent in proportion to the halftone dots. The plate is now immersed in an acid bath that will etch the plate. The result is a relief image that resembles a rubber stamp. The plate is locked into a printing press and inked. The inked plate is pressed against printing paper. The ink transfers to the printing paper and the result is a printed catalog ready to be mailed to perspective buyers. This process falls into the category of what is loosely called “lithography”.