Comparison Nikon Speedlight SB-910 vs Nikon Speedlight SB-900

The duration of the pulse of light provided by the flash. This indicator can range from thousandths to hundred thousandths of a second; it is usually expressed as a fractional number with a unit in the numerator, such as 1/880 s. The human eye does not notice the difference, but in some shooting modes it can become critical. For example, to capture fast-moving scenes (such as splashing water, the flight of an insect, or the movement of machine parts) you need to choose a flash with the shortest flash duration possible — otherwise the image may be blurry.

The longest pulse duration in modern photoflashes is about 1/800 s; the minimum value can reach 1/30,000 s or even less.