 
By definition, a luminary and an illuminated sign primarily differ because the former replaces or assists daylight in a defined space to aid human vision, while an illuminated sign strives to gain attention with light’s assistance, and then transmits a message.
从字面上理解，发光体和发光标识最主要的不同是发光体能让人类的视觉产生对光反应，而发光标识不仅仅像发光体一样让人们能够看到，并且可以引人注意，更多的是对人额外传递一种信息。
As lightsources, particularly LEDs, get smaller and brighter, many signshops seemingly neglect the sign’s main purpose; many current channel-letter signs are barely readable because their character properties don’t match the illumination level (Photo 1).
用光源举例来说，像LED又小又亮，有很多标识供应商似乎忽略了它的主要作用；现在有很多发光立体字只能很勉强的看清楚，因为字体的属性和光源发光的程度不匹配。
So what makes a sign readable? The yardstick is human ocular anatomy. At an optimum contrast level, the human eye can see two objects as separate if they reach the eye at an angle spacing of 1 arc-minute (1/60 of a degree). That equals a 1-in. separation at a distance of roughly 420 ft. If the object is too bright or dim, the eye resolution is easily reduced by a factor of 10 or more.
什么样的发光标识才能让人看清楚呢？这个尺度就是对人类视觉的剖析。在最佳的对比程度水平，人类的眼睛可以分辨两个物体时因为它们在人类的眼睛里有1弧分（一度的1/60）的角度空间。那相当于一英寸。间距的距离大约420英尺。如果物体太光或者太暗，人眼睛看上去的清晰度会减低十分之一或者更多。
If the surrounding environment is too bright, the human eye can’t focus well on intense lightsources, which causes a blurred impression. Fig. 1 shows the irradiating effect of blurring starts at different surface-brightness levels, depending on the environmental brightness level to which the eye is adapted. With characters, unfocused/blurred characters start at much lower levels than for plain lightsources. The contrast, including color contrast, of the characters to the background influences the readability from a distance too; some examples are given in Fig. 2.
如果周围的环境太光，人类的眼睛不能集中在强烈的光源里，因为这样会引起模糊的感觉。图1显示了在不同程度的亮度表面会对模糊度产生影响，并且要看眼睛对周围环境的亮度是否适应。在字里面，不清楚或者模糊的字母如果使用普通的光源清晰度会更低。与相比较，从距离包括颜色作为字母的背景会影响辨析能力，在图2有一些例子。
Character shape is another important parameter. Who hasn’t complained about their physician’s handwriting? (Sadly, proper handwriting isn’t taught at many schools anymore.) The more intricate and artistic the fonts are, the more difficult it is for the eye to decipher the message (Fig. 3). Usually, serif fonts’ varying stroke widths (like the widely used computer font “Times New Roman”) impair readability. However, some serif fonts, such as Courier, simplify character shapes and enhance the baseline, which leads the eye along the line of text (see Fig. 4 for dimensions of a line of text).
字母的形状也是另外一个重要的因素。 就像很多人都抱怨过医生写的字很潦草。（现在很多学校都没有专门教学生正确写字的课程）越是复杂和艺术的字体，就越难用眼睛辨认。（图3）通常，线衬字体有不同的笔画宽度（例如：电脑字体“Times New Roman”），这样会影响阅读的能力。但是有一些线衬字体：Courier，简单的字形并且提高了字形的基线，这样看的字体更一目了然。
The simpler the character shape, the faster the eye can recognize it; thus, sans-serif block letters are good, but, for best readability, use capital block letters only. Capital characters of the same total height give much better character recognition at a distance than lower-case characters, because no space is wasted above lower-case characters or undercuts. Also, the stroke width plays an important role. Strokes that are too thin or fat (strokes much wider than the gaps) don’t read well. At best, the line width should be roughly 1/6 to 1/5 the height of the capital letters (Fig. 2).
越是简单的字体，越是更容易地让人看的清楚。因此，加粗的无衬线字体最适合，当然，想达到最好的辨识效果还是用大写字母。在同一个距离，同样高的大写字母比小写字母更好辨认，因为没有小写字符空间上的浪费。同样，笔画的宽度也占据一个很重要的角色。笔画太细或者太粗（笔画比间距还粗）都会不好识辨。最好的效果，字间的距离应该是首写字母的六分之一至五分之一左右。
Character spacing, aka kerning, is roughly as important as stroke width in lit characters (Fig. 5). Proportional spacing (space width proportional to the width of both adjacent characters) saves space, but takes longer to read compared to constantly spaced fonts. If we put characters too closely together, the eye can’t distinguish in-character stroke separations from character separations.
字符的间距，又名字距，在点字符里面这和笔画的宽度一样重要。虽然比例间距（空间宽度与相邻字符的宽度成比例）减少空间，对比间距字体来说这样需要更多的时间辨认。如果我们把字符拼在一起太紧，这样会让眼睛不能区分从字符分离出来的笔画分离。例子如下：
Thisisthesameaswhenyoudontseparatewordsproperly.
For legibility, here’s how to estimate a font’s minimum required character height, based on a height/width ratio:
为了更好的理解，在这里告诉你基于高和宽的比例怎么测量一个字体所需最小的字符高度：
Min. Height (in in.) = distance (in ft.)/ (600 * h-to-w-ratio * contrast factor). The contrast factor varies between 2.0 (for black on yellow) and 0.2 (for yellow on red).
最小的高度（英寸）=距离（英尺）/（600*高和宽的比例*对比系数）。对比系数在2.0（黑与黄对比）至0.2（黄与红对比）之间变化。
In most local sign codes, sign sizes for illuminated signs are limited, depending on the city zones. So, the space permitted or available must be used effectively; less text is more. With the first electric signs (incandescents), irradiation/blurring posed problems. Although the light spots transformed into a more or less continuous blob of light, the shape of the characters disappeared. Frosted (or colored) lightbulbs helped reduce each individual spot’s brightness. Now, because modern LEDs are even smaller than an incandescent filament, the problem with too-small, too-bright spots persists (Photo 2). Even a standard, 20mA LED yields a local brightness of more than 10-15 million ft.-lamberts at the semiconductor crystal. Consequently, this lowers the local lightsource’s brightness below the level stated in Fig. 1, which implies great losses of light normally.
在不同的城市区域，大多数当地的发光标识的尺寸都是受到限制的。因此在允许的情况下，发光标识必须得到有效的利用，并且越少的文字越好。最开始的发光标识是用白炽灯发光的，容易出现照射模糊的问题。虽然光点转变成连续的光团，但是，还是没有变成字符的形状。磨砂灯泡（或彩色灯泡）可以帮助减少每个点的亮度。因为我们现在使用的LED比白炽灯还小，就会存在太小太亮的问题（图2）。尽管一个标准，在一个半导晶体里面20mA的LED的能产生局部1000万-1500万英尺朗伯德的亮度。因此，局部光源亮度低于规定的水平，这意味着光正常的亮度损失。
Because the environmental brightness of the sign must be considered, for signs installed inside shops and malls, the environmental light levels often can be assumed to be constant throughout the sign’s operation. Thus, for indoor signs, before estimating/quoting, measure the environmental light level to dimension the lighting system properly.
因为考虑到标识亮度在环境中的影响，对于在商店商场安装标识，都必需让标识在环境中灯的光亮水平达到一致。因此，在对室内标识做评估和报价之前，都要对环境灯光水平到
灯光系统，进行适当的测量。
For outdoor signs, measure the sign’s environmental light levels at dusk and during average night conditions. Then, position the sign brightness for optimum readability at the highest brightness level, and employ a smart-dimming system that reduces the sign brightness with decreasing surrounding light levels (and switch off the sign during no-traffic nighttime). Optimum readability in all shades of dusk is guaranteed, but this also provides the largest possible energy savings. Of course, the signface material’s transparency should be as high as possible. This, even with the higher investment cost, and the use of numerous small-power LEDs (compared to a few high-power ones per sign surface, which need heavier scattering and, thus, higher losses) - will yield the most economical solution in the long run.
对于户外的标识，通常在黄昏与夜间去测量标识的环境光亮水平。然后把标识最适合辨认度的亮度，调到亮度最高的水平，并且采用智能调光系统去减少标识的亮度，去降低周围环境的光亮水平（在没有交通的夜间关掉标识的发光）。在黄昏的色调环境，标识会有最适的辨认度，并且达到了最大的节能效果。当然，标识面材质的透光度应该尽可能的高。虽然投入比较高，并且用大量的小功率的LED（与每个标识面用少量大功率的LED产形成亮度的散射因而产生光的流失相比教），但是长期来说，这也是一个比较经济的方案。
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