It took a lot of research to invent panchromatic film. Up until about 1940, most films had problems in being sensitive to the whole range of colors. Most films

It took a lot of research to invent panchromatic film. Up until about 1940, most films had problems in being sensitive to the whole range of colors. Most films on sale were 'orthochromatic' which signified that they weren't sensitive to red, and so you could develop them in a darkroom with a red 'safelight'. It also meant that red showed up as black on the final photo. When I first started playing with photography in the mid 1950s, I killed several films while developing them because the books I was learning from assumed you were using 'orthochromatic' films but I was using the newer 'panchromatic' films. I soon learned that I needed to develop my films in total darkness, but I could still use a safelight when printing those black and white negatives, because the printing paper didn't need to be panchromatic seeing that it was only working with shades of grey.