Guide Numbers

[chilliz]

I am looking for a flashgun but I am a bit confused with guide numbers, can anyone tell me how these are worked out and what distances they relate to.

Thanks in advance

 

[DiddyDave]

The higher the number more powerful the flash, some offer zoom heads so can double or more their widest GN

The GN was used as a means of calculating exposure for any given ISO, distance, and power setting in the old 'manual' days

You don't need massive power to shoot most things, but a very powerful gun used at 1/2, 1/4, 1/16th setting recycles a lot faster than a lower powered on at full power

DD

EDIT - have a read here for guidance http://www.vividlight.com/Articles/1214.htm

 

[chilliz]

Thanks for the link DD, I shall have a read.