from this thread: http://www.controlbooth.com/forums/lighting/8629-blue-edge-brown-edge.html.'Dip'Oaldabs, I hope this helps.
The following contains some inferences based on experience and observation, but the historical facts are absolutely correct. Note I am speaking of professional designers working with union crew members and rental fixtures.
Before 1992, designers would focus a wash of ERSs by setting a sharp edge, making shutter cuts, and then running the barrel either slightly out or in to soften the edge. In theory, after the first light was focused, the designer and electrician knew the barrel setting for all the other lights. In practice however, the bench focus of the light played a major factor and sometimes one light would look better with barrel in, even though all of its brothers had barrel out. On order to speed the focus process, some clever designers took to focusing all units sharp, and then adding the lightest frost available at the time, R114.
When the SourceFour became the standard, the practice continued and escalated, as designers saw that the S4 beam was almost too perfect. It was difficult to obtain a soft edge that would blend with its neighbors. So the practice of adding Hamburg became even more commonplace. But never being satisfied, designers wanted a less soft edge than R114 afforded, but didn't want/couldn't to go back to running the barrel. Thus begat R119. After a few years, again designers decided they wanted something slightly less soft, and R132 was born. Choosing from three densities of Hamburg is still more efficient than having an IA guy run the barrel on every light, while 27 other stagehands look on.
It offends my sensibilities to think of putting frost in a template unit, so forgive me if I ignore that. I must ask if same designer also insisted on donuts?
"Frost" is a generic term which may be used to refer to any diffusion, not just R100. I've used the term "Hamburg" above when referring to all three R114, R119, R132. There are rough equivalents in Lee and Apollo. GAM is unique in that they offer 9 different degrees of diffusion, from 10-10 to 10-90. I'm still searching for the perfect diffusion for my followspots. See http://www.controlbooth.com/forums/lighting/5772-ever-put-baggy-followspot.html?highlight=baggy.
For a garage experiment, sharp focus an S4, with shutter cuts. Run the barrel and observe the edge. Put it back to sharp. Now try 114, 119, and 132. Post your findings! Obviously the desired edge will vary depending on the fixture's intended purpose, so this exercise is an abstraction. And we have yet to touch on peak vs. cosine distribution.
Most of the designers that come through my theatre don't spec diffusion. They would tell you that it is a mark of a lazy or a Yale designer. Point, cut, blend. That is how we do it. When done right, I think you can get a better blend with more lumens on stage if you get your edge through focusing the fixture rather than using diffusion. ...
Do you mean when:When making a generic plot with areas...
Great article Derek!
I do it for several reasons...
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