Question

Why does the monitor need Gamma correction?

Answer 1

The need for gamma correction in displays is primarily related to the characteristics of the human visual system, the efficiency of signal transmission and storage, and the accuracy of image display. The following is a detailed explanation:

1. The human eye's perception of brightness is nonlinear.

The human eye is much more sensitive to details in dark areas than details in bright areas. For example, in dim conditions, the human eye can detect very subtle changes in brightness; in bright light, however, changes in brightness have relatively little impact on vision.

This nonlinear perceptual characteristic can be described by the Weber-Fechner law: the brightness changes perceived by the human eye are proportional to the logarithm of the actual physical brightness, not a linear relationship.

2. Mathematical Definition of Gamma Correction

Gamma correction adjusts the relationship between the input signal (such as image pixel values) and the output brightness using a power function. The formula is:

V_out = V⁷_in

Where $\gamma$ is the gamma value (typically 2.2 or 1.8).

Gamma < 1: Dark areas are boosted and bright areas are compressed (used for encoding to save bandwidth).

Gamma > 1: Dark areas are compressed and bright areas are boosted (used for decoding to restore linear brightness).

3. Historical Reasons: Physical Characteristics of CRT Displays

The electron gun emission intensity of early CRT (cathode ray tube) displays exhibited a nonlinear relationship with input voltage (γ ≈ 2.2), resulting in output brightness that was not proportional to the input signal.

To compensate for this, gamma encoding (γ ≈ 1/2.2) was pre-applied to images before storage or transmission, making the final displayed brightness closer to linear.

4. Compatibility and Standard Harmonization of Modern Displays

Although modern displays like LCDs and OLEDs have a closer physical response to linearity, gamma correction standards (such as γ = 2.2 for the sRGB color gamut) are still used to maintain compatibility with historical content (such as movies and photographs).

Without correction, images appear too dark on the display, and dark details are lost.

5. Optimizing Signal Transmission and Storage Efficiency

Gamma encoding compresses dark signal levels, reducing data size and improving transmission efficiency. For example:

In an 8-bit image (256 grayscale levels), dark details may occupy only a few shades under linear encoding, while gamma encoding distributes details more evenly. This feature is particularly important in older systems with limited bandwidth.

6. Practical Applications

Photography and Photo Editing: Uncalibrated displays can cause photos to appear distorted in brightness when printed or shared.

Games and Film: Gamma correction ensures detail in dark scenes (such as shadows and night scenes) is visible, enhancing immersion.

Design: Designers must work on gamma-calibrated displays to ensure consistency across devices.

Summary

Gamma correction uses nonlinear adjustments to compensate for the perceptual characteristics of the human eye, physical imperfections of displays, and historical standards, ensuring images are displayed with accurate brightness and rich detail. It bridges the gap between digital signals and human vision and is crucial for cross-device content consistency.

Answer 2

Monitors require gamma correction because it can correct the nonlinear response characteristics of display devices and ensure linear restoration of image brightness. The human eye is sensitive to dark areas. If not corrected, the monitor will compress dark details in a nonlinear manner, resulting in dark areas that are too dark, bright areas that are too bright, and color and level distortion. Gamma correction compensates for the inherent curve of the monitor by adjusting the power function relationship between the input signal and output brightness (such as a gamma value of 2.2), so that the final displayed brightness linearly matches the original signal, restoring the light and dark transitions and color details of the real scene.

Especially in professional design, film and television production, gaming and other fields, monitors that have not been gamma-corrected can mislead creators' judgment of color and light and shadow, affecting the final presentation of the work.

Modern operating systems and graphics cards generally support automatic gamma correction, and users can also manually adjust through the monitor menu or a colorimeter to obtain a more accurate visual experience. In short, gamma correction is a key step in eliminating nonlinear distortion of display devices and ensuring true image restoration.

Answer 3

LED displays require gamma correction to adjust their brightness response curves to conform to the human eye's nonlinear perception of brightness, thereby optimizing display effects, improving contrast, and eliminating brightness distortion. The core formula is V_out = V^y_in

(γ is usually set to 2.2).

Answer 4

LED displays require gamma correction to adjust the brightness response curve to conform to the human eye's nonlinear perception of light intensity (usually the gamma value is set to 2.2). This solves problems such as dark or bright images, loss of detail in dark scenes, and ensures consistent color performance across different devices.