IIRC, the resists I have used are sensitive in the blue-to-medium-UV
range.  In the past I've used a bright #2 photoflood bulb with good
results exposing KPR negative resist.  The positive-acting resists
seem to like a bluer source such as carbon arc, etc.
Commercial "black light" flourescents work well, too.

> what frequency is photo-resist of the UV type most responsive too?
>
> Would it fall into the UV-C range?