User interface systems for head-worn computers

A head-worn computer, comprising:

• a frame mechanically adapted to position a see-through optical computer display in front of a user's eye, wherein the frame includes an arm adapted to hold the frame to the user's head;
• a rotary dial mounted on the arm and accessible to the user;
• a selection device mounted on the arm proximate the rotary dial;
• and
• the rotary dial adapted to control a volume of the head-worn computer's audio system and further adapted to control a brightness of content presented in the see-through optical computer display, wherein the selection device controls whether the volume or brightness are controlled by the rotary dial.