Macro Ring Flash: Test

Ages ago I bought a small ring flash which also had led lights.  The first trials revealed its flash wasn't very powerful, but then again it wasn't very expensive.  The led lights provided enough light to make it useful for macro photography. Today I decided to check if the flash's guide number accordning to the specs (15) was correct and located another ancient device - the flash light meter.  A very surprising result: Guide number = Zero.  The "flash" doesn't have a flash.  It just turns on the led lights for a very short time.

But I have a plan...