Continued from January  2011 CTI Newsletter

Why Use Half Top Hats?

First, let's have a quick  refresher class in top hats.  If you look up in any Broadway or West End theatre you'll see top hats on nearly every conventional fixture. Why are they used?

Designers use top hats for three primary reasons:

1.  To decrease the viewing angle to the lens so the audience doesn't see the bright and potentially distracting source of  light.
2.  To block spill light caused by optical deficiencies in the lighting fixture.
3.  For decorative purposes, e.g., to make a lighting fixture look more "theatrical." Concentric rings, egg crates, and cross baffles are often used for this purpose. 

Those three reasons illustrate the concept of  why designers use top hats, but why are half top hats used?   For half top hats, the first three reasons are the same, but there is an important fourth reason:  To make a lighting fixture "disappear" in the lighting rig.  This is easy to see in a theatre or light lab.  

Here is a Source Four in a lighting rig:

It's easy to see that the bright glow of the lens might be distracting to the audience.  Logic would suggest that the designer might choose to use a top hat to "decrease the viewing angle to the lens," in other words, to hide the bright glow of the lens from the audience.  Click here to add a full top hat.