3 Common Shading Mistakes_三個常見著色錯誤 by Dorian Iten

Reference_3 Common Shading Mistakes

One of the secrets of the old masters is capturing light.

老一輩大師捕捉光的秘密

It is also one of the main struggles of the aspiring artist. The goal of this article is to explain an important principle about how light works: the relationship between inclination and brightness. This will help you bring your work to life with a sense of light. And it will help steer clear of the three most common shading mistakes.

這也是有抱負藝術家主要努力的地方。這篇文章的目標是解釋有關光是如何運行的原則 : 傾斜度和亮度的關係。運用光感讓你的作品提升，也可以避開最常見著色的三種錯誤。

Form Light 形體光

The part of an object that receives direct light is called the form light. For the purpose of this article, we will focus on this area and see what exactly is happening with the shading.

物體接收直線光的部分就叫形體光。本文的目的，我們將探討這塊，觀察著色是如何發生。

What we are concerned with, is the change of brightness within the form light area. As the form turns away from the light source, it gets darker. These different tonal values are called halftones. They are generally grouped into light halftones and dark halftones. You will see why that is below.

我們關切於在形體光區域改變亮度，當形體遠離光源，它會變暗，這些不一樣的色調，稱為半色調。他們一般由亮半色調和暗半色調組成，你可以從下圖知道為什麼。

​Light on a flat plane光在平面上

The brightest area of any surface is where it faces the light directly. As the surface turns away from the light source, it gets darker. Here is an example of a simple plane. It's noon and the sunlight is coming straight from above. Explore how the plane's brightness changes as the plane spins.

任何表面最亮的部分，就是直接面向光源的地方。當表面轉離光源，會變暗，例如一塊平面，在中午時間，陽光直射在上頭，把平面旋轉，探討平面亮度的改變。

Guess Relationship猜測關係

Your turn! Make a guess. What is roughly the relationship between the inclination of the plane and its brightness? Use your intuition. We'll check the results in a moment.
換你了! 猜看看，平面傾斜角度和它的亮度大概是甚麼關係?運用你的直覺，我們等一下看結果。

Fill in the table below.​

INCLINATION	BRIGHTNESS
0°	100%
10°	%
20°	%
30°	%
40°	%
50°	%
60°	%
70°	%
80°	%
90°	0%

Making sense of nature解釋自然

If your intuition about this is like that of most, you will have assumed a light falloff that is close to linear. (100%, 90%, 80%, 70%… etc.) It's a good guess, but this is exactly where most of us get blindsided. In the real world, things behave differently.

如果你的直覺跟大多數人一樣，會假設燈光衰弱會趨近於線性(100%, 90%, 80%, 70%… etc.)，猜得好，但這正是我們的盲點所在。在真實世界中，事物以不同方式運作。

Here is what is really happening. Light falloff is not linear. Instead, it follows a nonlinear falloff. There are different ways of calculating this, but Johann Heinrich Lambert’s Cosine Emission Law is a popular method and a good approximation.

而真相是甚麼？光的衰減並非線性，而是非線性衰減。有不一樣的方式計算光現衰減，但是比爾-朗伯定律是最普遍的方式和一個不錯的近似值。

Here are the actual numbers, compared to your guess:

這是實際數值，和你猜測做比較

Click here to reveal solution

INCLINATION	YOUR GUESS	ACTUAL BRIGHTNESS
0°	100%	100%
10°	90%	99%
20°	80%	97%
30°	70%	94%
40°	60%	89%
50°	50%	82%
60°	40%	73%
70°	30%	62%
80°	20%	45%
90°	0%	0%

Sphere Example 球體案例

And this is what it looks like on an actual object. Switch between linear falloff and Lambert’s cosine emission law. Which one creates a stronger sense of light?

這是它在真實物體上看起來的樣子。線性漸變和比爾朗伯定律，哪一個創造了較強列的光感?

Slide the toggle.

Linear  Lambert

Lambert 比爾朗伯定律


Linear 線性漸變

Common Shading Mistakes

常見的上色錯誤

In order to keep a strong sense of light, the best strategy is this:
為了保持有說服力的光照，最好的策略如下:

• Keep the light halftones light and the value changes subtle.
• 保持亮半色調的光和亮度細微地變化
• Make the dark halftones dark enough.The change in brightness gets more dramatic the closer you approach the terminator, where light turns into shadow.
• 讓暗半色調有足夠的暗，光照的變化，越接近光照轉成陰影的地方，會更具戲劇效果。
• Keep the reflected lights subtle. Don't make them too bright. We'll look at this in another article in the future.
• 保持微亮的反射光，不要太亮，這我們會在未來其他文章討論。

Here are the three mistakes I see most often:

這是我常看到的三種錯誤 : 

I hope this was helpful! On your next drawing, apply what you’ve learned today!
希望這有幫助 ! 下次你在畫畫時，可以利用今天你所學的!

Happy drawing,
Dorian

快樂地畫圖
Dorian