Dynamic Photometric Area Selection for Backlight Exposure Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional imaging systems face challenges in accurately setting photometric areas for exposure control, particularly in environments with varying lighting conditions, leading to inappropriate exposure adjustments that can result in underexposed or overexposed images, especially when capturing human faces in back-lighting scenarios.
Innovation Solution
The system employs a custom photometric mode that dynamically sets the photometric area by calculating the average luminance values of detected face or human body areas and dividing the image into blocks to identify areas with minimal luminance change after exposure adjustment, ensuring accurate exposure control by selecting areas with luminance differences within a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photometric area setting methods are used, then the system is simple to operate, but exposure control accuracy deteriorates in varying lighting conditions
Solution Approach 1:
The image is divided into multiple blocks, and face detection is performed on each block to identify appropriate photometric areas. This segmentation approach enables accurate exposure control by selecting from multiple candidate regions rather than using a single fixed photometric area.
Solution Approach 2:
Face detection and luminance calculation are performed in advance to determine suitable photometric areas before exposure control is executed. This preliminary analysis ensures that the correct photometric areas are identified and selected prior to applying exposure adjustments.
2Reliability
If fixed photometric areas are used, then the system is simple to control, but image quality deteriorates due to underexposure or overexposure
Solution Approach 1:
The photometric area selection is made dynamic by detecting faces in divided blocks and calculating luminance values to adaptively determine the most appropriate photometric areas. This dynamic approach allows the system to automatically adjust to varying lighting conditions and subject positions, ensuring consistent image quality without requiring manual intervention.
3Measurement precision
If manual photometric area selection is used, then exposure control precision can be high, but processing time increases
Solution Approach 1:
The image is divided into multiple blocks for parallel face detection and luminance calculation, which enables efficient processing while maintaining precise photometric area selection. This segmented approach allows the system to analyze multiple regions simultaneously rather than sequentially.
Solution Approach 2:
The system automatically performs face detection, luminance calculation, and photometric area selection without requiring manual intervention. This self-service approach maintains high precision in photometric area selection while eliminating the time cost of manual operation.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A control apparatus includes a detection unit configured to detect an object area in an image captured by an image capturing apparatus, a dividing unit configured to divide the image into a plurality of divided areas, a first calculation unit configured to calculate a luminance difference as a difference between a luminance value of the object area and a luminance value of each of the divided areas after the image capturing apparatus executes exposure control by setting the object area as a photometric area, a second calculation unit which calculates a first amount of change as a difference between luminance values of the object area before and after the image capturing apparatus executes exposure control and a second amount of change as a difference between luminance values of the divided area before and after the image capturing apparatus executes exposure control, and a determination unit which determines a photometric area.