Using a small, flat, apparently directionless (on same axis as lens) ring light...just the thing to flatter folks in their portraits (NOT!)
(I know this is much too late, one year after the message was posted posing the question, but hopefully it will stop others from considering for this application!
I respect your opinions and experience. I feel compelled to disagree. Shutting down creative exploration is not, in my opinion, helpful. In this particular case, there are plenty who would respectfully disagree.
I don't personally tend to use ring light as the key light for portraits.
But there is a trend, which goes in and out of fashion, to do exactly that. Some people do it well and it is often popular. There is nothing wrong with a person pursuing this goal.
Ring light is a superior choice for a fill light, in my experience.
It has a well established tradition in macro and extreme close up applications.
I have seen a number of creative applications.
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