This is kind of an odd approach but what the hell...
This requires some prior knowledge but... In the past I have hired a variety of developers across many languages and sometimes languages popup which are so specific that I may not know how to immediately glean if someone is competent. What I did was contact some industry professionals, who knew more than I, to get some templated questions and answers. That way I can talk to someone on the phone during an interview and drop these questions out that seem like I'm very knowledgeable. If someone on the phone balks at a question, I just need to be able to realize that they are back peddling... I'll have a roundabout answer to base my conclusion off of to tell if they really do at least know _something_ that's more indepth...
This won't weed out the photographers who really know what they're doing but it should at least help weed out some of the trash
Long answer and I know it's in a completely different setting but I think there's at least something valuable in there you may be able to use to your advantage.
Best of luck!