KS3 Cambridge Media: Essential Formulas and Theorems Quick Reference Manual | KS3 剑桥媒体：公式定理速查手册

📚 KS3 Cambridge Media: Essential Formulas and Theorems Quick Reference Manual | KS3 剑桥媒体：公式定理速查手册

This quick reference manual is designed for KS3 Cambridge Media students. It compiles the essential formulas, theorems and conceptual models that underpin media analysis and production. From exposure triangles to narrative structures, mastering these core ideas will strengthen your practical skills and critical thinking.

本速查手册专为 KS3 剑桥媒体课程学生编写，汇集了支撑媒体分析与制作的核心公式、定理和概念模型。从曝光三角到叙事结构，掌握这些核心思想将提升你的实践技能和批判性思维。

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1. The Exposure Triangle Formula | 曝光三角公式

In photography and videography, correct exposure is achieved by balancing three variables: aperture, shutter speed and ISO sensitivity. The relationship can be expressed as a proportional formula.

在摄影和摄像中，正确曝光是通过平衡三个变量实现的：光圈、快门速度和 ISO 感光度。它们的关系可以用比例公式表示。

Correct Exposure ∝ f⁻² × Shutter Time (t) × ISO/100

f-stop is the aperture value; smaller numbers (e.g. f/2.8) indicate a wider opening. Shutter time is measured in seconds or fractions of a second. Raising any variable increases the light captured. For example, doubling the ISO from 100 to 200 has the same brightening effect as doubling the shutter time.

f 值是光圈数值；较小的数字（如 f/2.8）代表更大的开口。快门时间以秒或几分之一秒计量。增大任意变量都会增加进光量。例如，将 ISO 从 100 提高一倍到 200，与将快门时间延长一倍，对亮度的增强效果相同。

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2. Rule of Thirds Theorem | 三分构图法则定理

The Rule of Thirds divides the frame into nine equal rectangles using two horizontal and two vertical lines. Placing key subjects along these lines or at their intersections creates a more balanced and engaging composition.

三分法则通过两条水平线和两条垂直线将画面分成九个相等的矩形。将关键主体放置在这些线条上或它们的交叉点处，能创造更均衡、更吸引人的构图。

This theorem states that the four intersection points (power points) naturally draw the viewer’s eye. For a landscape, placing the horizon on the upper or lower third line strengthens visual interest.

该定理指出四个交叉点（兴趣点）能自然吸引观者视线。对于风景，将地平线放在上方或下方的三分线上可以增强视觉张力。

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3. The 180-Degree Rule | 180 度轴线规则

When filming a scene with two subjects, draw an imaginary line (the axis of action) through them. The camera must stay on one side of this line to maintain consistent screen direction.

拍摄有两个主体的场景时，在它们之间画一条假想线（动作轴线）。摄影机必须保持在这条线的一侧，以维持屏幕方向的一致性。

If the camera crosses the line without a cutaway or neutral shot, the subjects will appear to swap positions, confusing the audience. The rule can be expressed as: Camera Angle stays within 180° arc.

如果摄影机在没有插入镜头或中性镜头的情况下越过轴线，主体看上去会交换位置，使观众困惑。该规则可表达为：摄影机角度保持在 180° 弧内。

Allowed Camera Angles: 0° to 180° on one side of the axis

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4. Depth of Field Formula | 景深计算公式

Depth of field (DoF) is the distance between the nearest and farthest objects that appear acceptably sharp. It depends on aperture (f-number N), focal length (f) and focus distance (u).

景深是指最近与最远被摄体之间可接受的清晰成像范围。它取决于光圈（f 值 N）、焦距（f）和对焦距离（u）。

DoF ≈ (2 × c × N × u²) / f²

where c is the circle of confusion (a sensor-dependent constant). A larger f-number (small aperture) and shorter focal length give deeper DoF. Doubling the focus distance quadruples the DoF.

其中 c 是模糊圈（一个取决于传感器的常量）。更大的 f 值（小光圈）和更短的焦距会产生更大的景深。对焦距离加倍，景深变为四倍。

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5. Screen Size and Viewing Distance Ratio | 屏幕尺寸与观看距离比值

For comfortable viewing, the distance from a screen should be proportional to its diagonal size. The recommended ratio varies with resolution and content type.

为获得舒适观看体验，与屏幕的距离应与其对角线尺寸成比例。推荐比值随分辨率和内容类型而变化。

Viewing Distance = Diagonal Size × (1.5 to 2.5)

For a 50-inch TV, optimal seating is 75 to 125 inches away. A cinema-like experience uses a smaller multiplier (1.2–1.5), while standard TV viewing leans toward 2.0–2.5.

对于一台 50 英寸电视，最佳座位距离是 75 到 125 英寸。影院式体验采用较小的倍数（1.2–1.5），而标准电视观看偏向 2.0–2.5。

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6. The Three-Act Narrative Formula | 三幕叙事公式

Most screen stories follow the three-act structure: Setup, Confrontation and Resolution. This can be modelled as a formula of narrative progression.

大多数银幕故事遵循三幕结构：建立、对抗和解决。这可以建模为一个叙事推进公式。

Story = Act I (25%) + Act II (50%) + Act III (25%)

Act I introduces characters and the inciting incident. Act II escalates conflict through rising action. Act III delivers the climax and resolution. Timing matters: a 90-minute film typically places the first turning point around minutes 22–25.

第一幕介绍角色和激励事件。第二幕通过上升的动作升级冲突。第三幕带来高潮和解局。时间安排很重要：一部 90 分钟的电影通常将第一个转折点设置在 22–25 分钟左右。

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7. Uses and Gratifications Model | 使用与满足模型

This audience theory suggests that people actively choose media to satisfy specific needs. The model can be summarised with a four-part formula.

这一受众理论认为人们主动选择媒体来满足特定需求。该模型可用一个四部分公式概括。

Media Selection = f(Information, Personal Identity, Integration & Social Interaction, Entertainment)

Information: learning, seeking advice. Personal identity: reinforcing values, finding role models. Integration: connecting with others, social empathy. Entertainment: escape, relaxation, enjoyment. Each factor weights differently per individual.

信息：学习、寻求建议。个人身份：强化价值观、寻找榜样。整合：与他人联系、社会共情。娱乐：逃避、放松、享受。每个因素在不同个体中权重不同。

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8. Complementary Colour Theorem | 互补色定理

On the colour wheel, colours directly opposite each other are complementary. When combined in additive light mixing, they produce white or neutral grey.

在色相环上，彼此正对的颜色为互补色。在加色光混合中，它们结合产生白色或中性灰。

Colour A + Complementary Colour B = White (or Grey) Light

For example, red and cyan, green and magenta, blue and yellow are complementary pairs. In media design, using complements creates high contrast and visual impact. In colour grading, adding a colour’s complement neutralises unwanted tints.

例如，红与青、绿与品红、蓝与黄是互补对。在媒体设计中，使用互补色可产生高对比度和视觉冲击。在调色中，添加某种颜色的互补色可中和不需要的色偏。

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9. Digital File Size Formula | 数字文件大小公式

The uncompressed file size of a digital image or video frame is determined by pixel dimensions and colour depth. The basic formula is straightforward.

数字图像或视频帧的未压缩文件大小由像素尺寸和色彩深度决定。基本公式简单明了。

File Size (bytes) = Width × Height × Bit Depth ÷ 8

For a 1920×1080 image with 24-bit colour (8 bits per channel), each frame needs 1920 × 1080 × 24 ÷ 8 = 6,220,800 bytes ≈ 6.22 MB. Video multiplies this by frame rate and duration.

对于一张 24 位色彩（每通道 8 位）的 1920×1080 图像，每帧需要 1920 × 1080 × 24 ÷ 8 = 6,220,800 字节 ≈ 6.22 MB。视频还要乘以帧率和时长。

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10. Media Literacy Verification Formula | 媒介素养验证公式

Critical media literacy involves a simple but powerful verification process when encountering any media message. It can be remembered through a three-step formula.

批判性媒介素养要求在面对任何媒介信息时，运用一个简单而有力的验证过程。这可通过一个三步公式来记忆。

Credibility Score = Question × Verify × Reflect

Question: Who created this? What is the purpose? Verify: Check the source against multiple trusted outlets. Reflect: How might this message influence me or others? Applying this formula builds immunity to misinformation.

质疑：谁创作了这个？目的是什么？核实：对照多个可信渠道核查来源。反思：这条信息会如何影响我或他人？运用这一公式可增强对错误信息的免疫力。

Published by TutorHao | Media Studies Revision Series | aleveler.com

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