Definition of guide number in English:

guide number

Line breaks: guide num¦ber

noun

Photography
A measure of the power of a flashgun expressed in metres or feet.
More example sentences
  • 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: