一旦灯光设计师理解可用的装置的光束特性，有一个计划（在有照明键的形式），并具有剧场建筑和现有照明立场坚定的认识，那么他或她需要确定投影距离从照明领域，在舞台上的斑点。

Once the Lighting designer understands the beam properties of the available fixtures, has a plan (in the form of  having a lighting key) and has a firm understanding of the theatre architecture and available lighting positions, then he or she needs to determine the throw distance from the lighting areas to the spots on stage.

记住，我们看了生产首席女高音的照明键，我们就可以开始确定从灯光位置的投影距离。

Remembering the lighting key that we looked at for the production of Prima Donna, we can begin to determine the throw distances from the lighting positions.

Lighting Key for production of Prima Donna

例如：让我们开始计划进入该领域的照明从舞台左侧为45度的前灯（标记为“中性反射光的键）的光。

For example:  Let’s begin by planning the light coming into the lighting areas from Stage Left as a 45 degree front light (labeled “Neutral Bounce Light in the key).

Plan View showing the throw of a 45 degree SL front light

图示的阶段与图站在中心线只是几英尺的舞台后部的石膏线的一部分的平面图。一看这个计划年轻设计师将被原谅认为它表明从照明仪器的身影28 1/2的投影距离“。然而，这远远大于实际的投影距离短。什么是不占在平面图中是这增加了抛距舞台上方夹具的高度。

The drawing to the left shows a plan view of a portion of the stage with a figure standing on the center line just a couple of feet upstage of the plaster line.A young designer looking at this plan would be excused for believing that it shows a throw distance of 28 1/2′ from the lighting instrument to the figure.However, that is far shorter than the actual throw distance.What is not accounted for in the plan view is the elevation of the fixture above the stage which increases the throw distance.

Section View of the stage through the center line

图示通过中心线的部分。注意，该剖视图显示了照明区在演员的脸的水平（舞台地板上述从5'至6'）计算出的占事实提供照明，使得观众可以看到演员的脸和特点一个的照明设计师的主要目标。同样，一个年轻的设计师可能会原谅认为这个图表明，从夹具图中的投影距离为33“。但是，再次，这是不准确的评估。此而剖面视图并准确地描述夹具的标高，它不考虑该器械被放置相对于所述中心线的角度。

The diagram to the right shows the section through the center line.Notice that the section view shows that the lighting area is calculated at the actor's face level (from 5′ to 6′ above the stage floor) to account for the fact that providing illumination so that the audience can see the actor's face and features is one of the main goals of the Lighting Designer.Again, a young designer might be excused for thinking that this diagram suggests that the throw distance from the fixture to the figure is 33′.However, once again, that is not an accurate assessment.This while the section view does accurately describe the elevation of the fixture, it does not account for the angle that the instrument is placed with respect to the center line.

为了在计算投射距离考虑到这两种高度和角度设计，就可以建立部通过照明装置的掷的轴线绘制。这样的部分在左侧图显示，从所选择的位置上的掷应37'-8的范围内“。

In order to account for both elevation and angle in calculating the throw distance the designer might create a section drawing through the axis of the throw of the lighting fixture.Such a section drawing at left shows that the throw from the chosen position should be in the range of 37′-8″.

Section View drawn along the axis of the lighting angle

使用从前面的文章的信息，我们可以判断，一个19度的来源夹具四如图所示头梁位置（以0.31的倍增因子将在项目中心时11 1/2“直径脸上水平照明领域定位该图中。还请注意，如果在照明区域向上或向下移动的阶段，则投影距离会改变和照明区域的直径将变大（如果投影距离的增加）或更小（如果投影距离减小。）

Using the information from the preceding post, we can determine that a 19 degree Source Four fixture positioned as shown on the first beam position (with a Multiplication Factor of 0.31  will project a lighting area at face level of 11 1/2′ diameter centered upon the figure.  Notice also that if the lighting area moves up or down stage, then the throw distance would change and the diameter of the lighting area would become larger (if the throw distance increases) or smaller (if the throw distance decreases.)