Toronto. Once the media (glass plates, film) became fast enough for instantaneous outdoor photos, people began creating a means to make indoor photos. In most cases the lack of a bright light was the limiting factor and various means to ignite a magnesium powder mixture for a brief very bright light began. The big risk with the so called flash powder was fire – or burns – from too much powder for a given space space.
A photograph created by flash illumination was easy for the practiced eye to tell – over exposure near the camera, deep shadows slightly further back, high contrast, and little or no “modelling”.
A safer means of a brief bright light was eventually created in flash bulbs. Such accessories became a standard on the Graphic cameras used for press work. Post WW2 there was a surge in flashbulbs for amateurs as well. A colour coating meant even colour film would work. A blue filter coating allowed daylight colour film to be used indoors while the far less popular amber colour allowed indoor colour film to be used outdoors.
All this faded when inexpensive electronic flash was sold from about the 1960s on. In the meantime, the makers of flash bulbs strove to promote their products touting marginal or irrelevant differences as major steps making their products far more desirable.
For this GE ad on pp132, 133 in the October 22, 1956 copy of LIFE magazine, the idea of a smaller bulb (M2) with more light output suggested you would see a big difference by switching manufacturers. The smaller bulb base was not an issue – just buy a cheap converter to fit older flashguns!