fine-pitch threadcutting on thinwall tubing

Anyone here have the ability to thread thinwall metal tubing with fine pitch
threads (like camera filters). Inside as well as outside?

I at first imagined one needed really weird taps & dies, but it occurred to
me that maybe it's just done with a cuttign tool on a lathe.

Then the question is...how does one obtain the right diameter tubing? I
imagine there are a limited number of sizes, and metric is another problem.

Oh, by the way, the application is threaded tubes & spacers for optical
applications.

I found a machininst who does this stuff but it's frightening costly...so I
wondered if it is frighteningly difficult.

Thanks

Murray