Definition of guide number in English:
A measure of the power of a flashgun expressed in meters or feet.
- Such technical items as ‘guide numbers’ don't seem to matter any more.
- Unless you're shooting under those conditions, consider the guide numbers to be estimates.
- Small flashes have guide numbers ranging from 45-80, while large shoe-mount units will be up to around 130.
Definition of guide number in:
- British & World English dictionary