OK, there are a few things to let you know on this...
Terminology to be on the same page:
Areas - is the industry term for Zone this will allow you to communicate and understand when working with others
An area is typically defined by the field of light at a distance, this can differ in spaces due to location of the fixture.
What is trying to be achieved...
we are typically looking for a 10-12' ellipse per fixture
this ellipse is for left to right and for down stage to upstage focusing
what we do is overlap these ellipses l/r and d/u by 25% to assist in eliminating dark spots of the field of light produced by fixtures.
You mentioned 9 zones, typically you will have a downstage and upstage row then also have some middle areas.
I would recommend for you to reach out to some options to help you on site...
Contact a local theatrical supplier to come in and instruct you on lighting focus.
Contact a local college with a theater program to come in and discuss with you.
Reach out to another school in your Thespians group/District who may have more experience to be able to help you.
We are all trying to create better theater and willing to help others
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Jerry Onik
V.P. Theatrical Supplies and Equipment
Heartland Scenic Studio
NE
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