I recently collaborated with Tahlia Jade to create some fashion inspired portraits to play around with a new lighting toy that I bought - RoundFlash Ring Flash Adapter which I purchased from B+H Photo. It's basically a speed light mounted ring flash adapter, but actually works compared to the other smaller more junky ones such as the Ray Flash or Orbis.
But onto the photography side of things, here some of the images that we captured using just this ring flash, and they were all shot using the Nikon D3s + Nikkor 35mm f1.4G which I found to be the best lens to use to get that "fashion ring flash" sort of look, anything wider would also work as well, but anything tighter than 35mm and you lose that nice big ring catch light that you see in Tahlia's eyes.