Automatic HDR Exposure Bracket Determination via Luminance Threshold Testing
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Solution Overview
Problem
Existing high dynamic range (HDR) imaging processes require manual analysis and selection of exposure values, which is cumbersome and reduces the ability to quickly capture interesting scenes in real-time due to inadequate accounting for lighting variations across a scene.
Innovation Solution
An image capture device automatically configures a set of exposure values by iteratively modifying the exposure setting until no objects are overexposed, determining the minimum exposure value and computing a bracket of exposure values for HDR imaging, allowing real-time determination and capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual analysis and selection of exposure values is used for HDR imaging, then exposure accuracy can be assessed, but the process becomes cumbersome and reduces real-time capture capability
Solution Approach 1:
The system performs preliminary exposure testing by capturing a test image at a preliminary exposure value before the actual HDR capture. This preliminary action allows the device to determine appropriate exposure values in advance, eliminating the need for manual analysis after capture while ensuring accurate exposure selection for the final HDR image.
Solution Approach 2:
The image capture device automatically determines its own exposure values by analyzing luminance in test images and comparing against threshold values. The device self-configures the bracket of exposure values without requiring external manual intervention, thereby maintaining both accuracy and real-time capture capability.
2Productivity
If a fixed exposure value is used for image capture, then the capture process is simple and fast, but lighting variations across different areas of the scene cannot be adequately accounted for
Solution Approach 1:
The system dynamically determines exposure values based on scene luminance characteristics. Instead of using a fixed exposure value, the device adjusts the bracket of exposure values according to the specific lighting conditions detected in the scene, allowing adaptation to varying lighting conditions while maintaining capture speed through automated decision-making.
Solution Approach 2:
The system changes exposure parameters by determining a bracket of multiple exposure values rather than using a single fixed value. This parameter adjustment allows the capture of both bright and dark areas in high dynamic range scenes, with the specific bracket values being modified based on luminance analysis of test images.
3Reliability
If multiple images are captured for HDR processing, then dynamic range coverage is improved, but the complexity of selecting appropriate exposure values increases
Solution Approach 1:
The system uses feedback from luminance analysis of test images to automatically determine the appropriate bracket of exposure values. By comparing the measured luminance against threshold values, the device receives feedback about scene brightness characteristics and automatically configures the exposure bracket accordingly, eliminating the complexity of manual selection while ensuring reliable HDR capture.
Data Source
AI summary
In some embodiments, an image capture device receives a capture command to capture an image. Exposure adjustment operations are subsequently performed. These operations include determining that a first luminance indicated by first image data, which is obtained using a first exposure value, exceeds a threshold luminance. The operations also include decreasing, based on the threshold luminance being exceeded, the first exposure value to a second exposure value. The operations also include determining, from second image data obtained using the second exposure value, that a second luminance indicated by the second image data is less than the threshold luminance. The HDR setting of the image capture device is configured to include a bracket of exposure values, where the second exposure value is a minimum exposure value from the bracket of exposure values. The image capture device executes a capture operation in which an image bracket is captured using this HDR setting.