The result is a brilliance of light much higher than the lamp's wattage rating would suggest.
The trade-off is that the lamp has a very short service life of seldom more than ten hours.
Photoflood lamps were used by photographers and film makers as a continuous lighting source.
The ordinary lamp is replaced by a photoflood bulb whose intense light is easily visible on film (and if so required, is bright enough that it can form the sole illumination for the shot).
Note that in each case an ordinary 100 watt lamp is provided for comparison purposes.