Light Source Magnitude

Hi

i have come across a microscope light source which may be able to double as a ringflash/light. the actual light is circular 10 watt 240 volt fluorescent tube.

Before I order one is it possible to work out if it might be bright enough i.e. is there some formula to compare flash guide numbers with light bulb wattage.

Any advise will be appreciated

Wouldn't it be about the same as a 10watt energy saving bulb? i.e. about 60 watts tungsten.... so it would be like using a table lamp. Should be OK close up.

shim