Camera Flash Color Temperature Adjustment for Fluorescent Lighting
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Solution Overview
Problem
Achieving correct color balance in digital images is complicated when the color temperature of light sources changes, especially with fluorescent lighting, which can cause color casts within an image due to its continuous color variation, making it difficult to apply a single color temperature profile across an image.
Innovation Solution
A method is implemented where a digital camera collects data on the ambient light's color temperature distribution and sets the flash unit's color temperature to match the predicted ambient light condition at the time of capture, ensuring accurate color balance by using a time-varying color spectrum model generated from calibration images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single color temperature profile is applied to an image, then the processing is simple and fast, but the color balance is inaccurate when light source color temperature changes
Solution Approach 1:
The image is divided into multiple regions (e.g., top, middle, bottom portions) and different color temperature profiles are applied to each region based on its specific color cast characteristics, allowing accurate color correction for each area while maintaining efficient processing
Solution Approach 2:
Instead of analyzing every pixel individually which would be computationally expensive, the method selectively analyzes representative regions of the image to determine color temperature profiles, achieving accurate color balance with reduced processing overhead
2Speed
If the exposure time is shortened to capture fast-moving subjects, then motion blur is reduced, but color variation within the image increases due to fluorescent lighting cycles
Solution Approach 1:
Different color temperature profiles are applied to different regions of the image (e.g., top portion vs. bottom portion) to compensate for the color variations caused by short exposure times under cycling fluorescent light, ensuring each region has accurate color balance
Solution Approach 2:
The system pre-determines multiple color temperature profiles corresponding to different phases of the fluorescent light cycle before image capture, allowing rapid selection and application of the appropriate profile based on the actual lighting conditions during exposure
3Measurement precision
If the color temperature profile is adjusted for each image individually, then color balance accuracy is improved, but the processing complexity and time increase
Solution Approach 1:
The system dynamically selects from a set of pre-determined color temperature profiles based on the specific lighting conditions detected in each image, rather than performing full individual analysis, thus maintaining high accuracy while reducing processing complexity
Solution Approach 2:
Multiple color temperature profiles are pre-calculated and stored before image processing, corresponding to different phases of the fluorescent light cycle. During image processing, the system only needs to identify which pre-calculated profile matches the current lighting conditions, significantly reducing computational complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate color correction across images captured under changing light conditions, including fluorescent lighting, by applying specific color balance adjustments to different regions of an image, ensuring consistent color rendition.
Implementation Method 1
The color temperature of the flash unit, such as an LED flash unit, is set to the identified color temperature
Data Source
AI summary
An approach is provided to adjust illumination color temperature at a flash unit of a camera. Data that corresponds to the ambient light of a physical environment is collected, such as at a color temperature meter included in the camera. The ambient light has a distribution of color temperatures that cycle over a fixed time period. When a flash request is received, a time is calculated at which the flash unit will flash. One of the color temperatures is identified from the distribution of color temperatures with the identified color temperature being the predicted color of the ambient light that will be present in the physical environment when the flash unit flashes. The color temperature of the flash unit is set to the identified color temperature.