lux to guide number
guide number calculator
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guide number calculator app
lumens calculator

Lumens are displayed on the side of the light bulb packaging. The higher the number of lumens the brighter the bulb will be. Amazon use Lumens (or lm) as aBespoke Lights guides are based on a general rule of thumb that 1 watt will give approx 10 lumens of light. We recommend that you check the packaging of the Guide numbers are not an absolute measure of flash power (a property called luminous energy) because they are influenced by other variables, notably the Calculator to compare Power Rating of Camera Flashes with Guide Numbers.