Light is expressed in Lumen. The higher the Lumen, the brighter the light
The run time is the amount of minutes at maximum strength. After the run time, the torch will shine for another couple of hours, however at a lower light capacity. The run time was measured at room temperature. Diving in colder water may decrease the run time.
A tortch with a narrow beam (spot) has a smaller beam angle, between 7 upto 20 degrees. You will be needing this is darker waters such as here in NL/BE. A torch with a broader beam (flood or wide) will illuminate a larger area. This type of beam is mostly used for photography and videography to make sure the light is evenly dispersed. A torch with an adjustable beam can be adjusted during a dive
A dimmable torch usually has 2 to 3 settings to dim the light. By dimming the intensity of the light you can extend the run time
