However, tripod threads were traditionally 1/4" and 3/8" British Standard Whitworth so you might find both Whitworth and UNC.
When I looked into it a while ago, I found one manufacturer using UNC and another using Whitworth. However, I suspect both use a cut profile optimized to fit either thread without binding.
There is not much between them other than a five degree difference in cut angle. Threads per inch are the same for both standards.