The pictures are like long exposures of manufacturing processes that show the best way to do the job. I cannot recall the name of these types of pictures, but I remember learning that a photographer had put lights on the hands of workers to identify the most efficient movements to complete a process. I also remember the whole idea being revolutionary to industry but I can't seem to find any pictures no matter how I frame my search on google. The reason I ask is that I recently acquired two of these pictures and I am wondering about the history tied to them. I know they came from DuPont and are probably from the 40s or 50s. Any idea of what they are called or where to find something to compare?
The term you're probably looking for is 'chronocyclegraphs'.
These were still images that, via the process you described, were used to analyse the degree of motion needed to complete particular work operations. The idea, based on Taylorist 'scientific management' principles, was that any reduction in the number of individual discrete motions needed to perform an operation would save on time and effort, and therefore cost.
The photograph process was developed by Frank Gilbreth but, to be honest, the pictures themselves are today little more than a historical curiosity. In contrast, a lot of the other work Gilbreth pioneered in this area, building on Taylor, continues to be used in the form of Time and Motion studies. These are about breaking a standard operation down into its component motions, which allows engineers to identify what actions are unnecessary ('non-value add') and how workplace layout can be optimised to reduce this waste (which feeds into Japanese concepts like 5S).
Operations Management (aka 'scientific management' aka Taylorism) often gets a bad rep and has had plenty of critics since its emergence in the early 20th C. But a lot of Taylor and Gilbreth's tools, methods and principles are still used today in industrial engineering.
Just not the chronocyclegraphs.