Some basic geometry using similar triangles

[Jay Barracato]

At some point I was told that the optimum angle for front lighting was 45 degrees to the performers. So what does this mean about mounting the lights, especially if you have a portable rig of trees or truss.

For ease of calculation let's imagine a 6 foot tall performer standing on the stage. Since both legs of a 45-45-90 right triangle are the same length, there is a point on the floor 6 feet behind the performer that creates a 45 degree angle.

Using that point as a vertex, a lighting bar 10 feet in front of the performer would be 16 feet from that vertex. That means the lights would have to be 16 feet above the plane the performer is standing on to achieve the 45 degree angle.

If the performer is standing on a stage and the lighting trees are on the floor, simply add the height of the stage.

I.e. The performer is on a 4 foot high stage, and the lights are 12 feet in front of where the performer stands, the lights would have to be 12+6+4 = 22 feet high to get a 45 degree angle between the performer and the lights.

If the performer is on a 2 foot high stage, and the truss is 6 feet in front of the performer, the lights should be 6+6+2 = 14 feet from the floor.

There will be a quiz next time, and no, I don't grade on a curve, I grade on a surface area...

 

[Rob Timmerman]

Re: Some basic geometry using similar triangles

At some point I was told that the optimum angle for front lighting was 45 degrees to the performers. So what does this mean about mounting the lights, especially if you have a portable rig of trees or truss.

In reality, all it means is that if you are ground supported, your lights are probably too low...

Also, don't forget about the 45 degrees out from centerline in addition to the 45 degrees up. Think corners of a cube.

 

[Tim Weaver]

Re: Some basic geometry using similar triangles

Also don't forget that it's just a suggestion. There are a myriad ways to light a performer. Some of those ways have light at 45 degrees....

 

[mackerr]

Re: Some basic geometry using similar triangles

Also don't forget that it's just a suggestion. There are a myriad ways to light a performer. Some of those ways have light at 45 degrees....

The book that defined the 45º angle was "A Method of Lighting the Stage" by Stanley McCandless. It was a standard text when I was studying theatrical lighting in collage. It was not The Method for lighting the stage.

In lighting bands it may be more important to get side and backlight than front light. Dramatic color from back and sides with some no color white light specials.

Mac

 

[Jay Barracato]

The book that defined the 45º angle was "A Method of Lighting the Stage" by Stanley McCandless. It was a standard text when I was studying theatrical lighting in collage. It was not The Method for lighting the stage.

In lighting bands it may be more important to get side and backlight than front light. Dramatic color from back and sides with some no color white light specials.

Mac

I was really just demonstrating an application of middle school geometry other than "how tall is the true?"

While I have lit performers in many ways, some recommended and some not, I will say the lower front lights are the more likely performers are going to complain about not being able to see.

 

[TJ Cornish]

Re: Some basic geometry using similar triangles

In reality, all it means is that if you are ground supported, your lights are probably too low...

+1.

For me, a room with 16' ceilings is a luxury - I do lots of hotel ballrooms where some ceilings are as low as 11'. My stages are usually 1 - 2', not 4, which helps, but I still end up putting my truss or tree stands pretty close to the stage, and work with mostly very wide fixtures - 36° and 50°, and am usually very happy if I can get 30° in either plane.