This is my second time in USITT, the theme for this year is about the evolution of technology and design in the past five decades. I really look forward to the sessions as well as the exhibition of the design from famous designers about their own progress.

We arrived at Kansas City yesterday afternoon, on the flight a student from SUNY Fredonia who sat next to me. He said Fredonia also have a large student group coming to the convenience. We are going to meet the whole group tomorrow in the Upstate New York USITT meeting.

I went to the “So you think you know everything about Top Hats” that is a lab session that demonstrate the use of and the need of top hats. Basically is the same section from last year but providing a more theoretical and mathematical way of explaining 45 degrees cutoff. If you do not quite understand what and why top hats is important, top hats can reduce the viewing angle to the lighting source that can be annoying or distracting to the lighting designer that it is possible that there is spill light to the auditorium and we see shadow of the audience. The 45 degrees cutoff is that the length of the top hat always equals aperture to achieve the angle.

Reasons that creates light spill is the fixture mechanical design, especially some less sophisticated optical like PAR or Fresnel also dust, haze and poor maintenance. Other reason is it can be a decorative accessory.

Here are some images of different top hats:

(the speaker also consider barndoor as one kind of top hat too)