A big issue with these things is that a lot of people get low-cost ring-lights that are really just a bunch of LEDs. Some of them are so dim they don't even publish their guide number, or the guide number isn't anything close to the amount of light from a real flash. If you're hoping to do macro shots, then you'll need a lot of light to allow small apertures that give you more DOF, and you want to use real flash with a pretty high guide number.
|Morning At Picture Lake by Buzz Lightyear|
from Dawns first rays
|AT-6 Harvard by jarud|
from Trainer aircraft
|Matterhorn by ewng|