This tool is an image and video editing calculator that adjusts the brightness and luminance of digital images. You use this calculator to apply a process called gamma correction, which changes the intensity of an image’s pixels. This is important because human eyes perceive light non-linearly, meaning we are more sensitive to changes in dark tones than in bright tones. Similarly, digital displays like monitors have their own inherent brightness curves. The calculator helps to correct these differences, ensuring that an image appears natural and consistent to the human eye, regardless of the device it is viewed on. By inputting a color value and a gamma setting, you can precisely control the brightness and contrast of your visual content.
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1. Main Formula
The primary formula for gamma correction adjusts a color value based on a specified gamma factor.
Main Formula
Corrected Value = (Original Value) ^ (1 / Gamma)
Explanation of Variables
Original Value: The input color value. This value must be normalized to a range between 0 and 1 before the formula is applied.
Gamma: The gamma value you want to use for the correction. A gamma greater than 1 makes the image darker, while a gamma less than 1 makes it lighter. A gamma of 1 results in no change.
Corrected Value: The output color value after gamma correction. This value will also be in the 0 to 1 range.
2. Supporting Formulas for Practical Application
To use the primary formula, you must first prepare the color values and then convert them back to their standard format after correction. This typically involves an 8-bit color depth (0-255).
a) Normalization Formula (Before Gamma Correction)
This formula converts a standard color value (e.g., from 0-255) into the required 0-1 range.
Formula
Normalized Value = Original Color Value / Maximum Color Value
Example for an 8-bit color:
Normalized Value = Original Color Value from 0-255 / 255.0
b) Denormalization Formula (After Gamma Correction)
This formula converts the corrected value from the 0-1 range back into a standard color value (e.g., 0-255).
Formula
Final Color Value = Corrected Value from 0-1 * Maximum Color Value
Example for an 8-bit color:
Final Color Value = Corrected Value from 0-1 * 255.0
Complete Workflow for a Single Color Channel
Start with an original color value (e.g., Red = 150).
Normalize the value: Normalized Value = 150 / 255.0 = 0.588
Apply Gamma Correction using your chosen gamma (e.g., Gamma = 2.2): Corrected Value = (0.588) ^ (1 / 2.2) = 0.798
Denormalize the value: Final Color Value = 0.798 * 255.0 = 203 (rounded)
Common Gamma Values and Their Effects
This table provides a quick guide to understanding how different gamma values will affect your image. You can use it to choose the right gamma setting for your specific goal.
| Gamma Value | Effect on Image | Common Use Case |
| 1.0 | No change | Linear color space, raw data processing. |
| 1.8 | Makes image lighter | Historical standard for some Apple systems. |
| 2.2 | Makes image darker | Standard for sRGB color space, used by most monitors and the web. |
| 2.4 | Makes image even darker | Standard for television and cinema (Rec. 709). |
| > 2.4 | Makes image significantly darker | Used for specific display calibration or artistic effects. |
| < 1.0 | Makes image significantly lighter | Used to brighten very dark images or for artistic effects. |
Example
Let’s use the calculator to apply gamma correction to a full RGB color. Imagine we have a dark blue color and we want to make it appear correctly on a standard monitor.
Scenario Details:
- Original Color: A dark blue with RGB values (R: 25, G: 40, B: 100)
- Target Gamma: 2.2 (standard for web and sRGB)
Calculation Steps:
- First, we normalize each color channel to a 0-1 range by dividing by 255.
- Normalized Red = 25 / 255.0 = 0.098
- Normalized Green = 40 / 255.0 = 0.157
- Normalized Blue = 100 / 255.0 = 0.392
- Next, we apply the main gamma correction formula to each normalized value.
- Corrected Red = (0.098) ^ (1 / 2.2) = 0.354
- Corrected Green = (0.157) ^ (1 / 2.2) = 0.443
- Corrected Blue = (0.392) ^ (1 / 2.2) = 0.655
- Finally, we denormalize the corrected values back to the 0-255 range by multiplying by 255.
- Final Red = 0.354 * 255.0 = 90 (rounded)
- Final Green = 0.443 * 255.0 = 113 (rounded)
- Final Blue = 0.655 * 255.0 = 167 (rounded)
The original dark blue color (25, 40, 100) becomes a much brighter blue (90, 113, 167) after applying a gamma correction of 2.2. This corrected color will appear more visually accurate on a standard display.
Most Common FAQs
Adjusting brightness typically shifts all the pixel values in an image up or down by the same amount. This can cause the darkest black areas to become gray or the brightest white areas to become clipped (losing all detail). In contrast, gamma correction adjusts the mid-tones of an image much more than it affects the very dark and very bright areas. This results in a more natural-looking change in luminance that better matches how our eyes perceive light.
A gamma of 2.2 became the standard largely due to the physical characteristics of older CRT (cathode ray tube) monitors. These displays naturally had a gamma of around 2.2. To make images look correct on these screens, people encoded the image files with an inverse gamma. This standard was then formally adopted for the sRGB color space, which is the most common color space used for web browsers, digital cameras, and PC monitors today. As a result, applying a gamma of 2.2 ensures consistency across the vast majority of devices.
Gamma correction directly affects both the brightness and the perceived color of an image. An image’s color is determined by the combination of its red, green, and blue (RGB) channels. Since gamma correction changes the intensity of each of these channels independently, it alters their balance. For example, lightening an image with gamma correction can make colors appear less saturated. Therefore, it is a fundamental tool for both color and luminance adjustments in digital imaging.