Dynamic Range Expansion for Blown-Out Highlight Detection
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Solution Overview
Problem
Users cannot determine the necessary dynamic range expansion to avoid blown-out highlights in images due to saturated signal values, making it difficult to suppress overexposure while maintaining a natural image appearance.
Innovation Solution
An image capturing apparatus and method that temporarily expands the dynamic range to detect signal values in blown-out areas, adjusts gamma correction characteristics to maintain a natural image appearance, and displays the required dynamic range expansion amount to the user.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dynamic range expansion is performed by underexposure and gamma correction, then blown-out highlights can be resolved, but the S/N ratio decreases
Solution Approach 1:
The system performs dynamic range expansion only in portions where blown-out highlights are detected, rather than applying it globally to the entire image. This partial application resolves highlights only where necessary, minimizing unnecessary signal amplification and preserving S/N ratio in areas where it is not needed.
Solution Approach 2:
The patent applies different processing to different portions of the image based on local conditions. By detecting blown-out highlights in specific regions and applying dynamic range expansion only to those regions, the system maintains local quality appropriate to each area - resolving highlights where present while avoiding degradation in other areas.
2Reliability
If dynamic range expansion is performed to resolve blown-out highlights, then highlight detail can be recovered, but the user cannot determine the necessary expansion amount due to saturated signal values
Solution Approach 1:
The system detects the presence and extent of blown-out highlights in the captured image and uses this feedback information to automatically determine the appropriate dynamic range expansion amount. The detection unit identifies saturated portions, and the control unit calculates the necessary expansion to resolve highlights while avoiding over-correction, providing automated feedback-based control.
Solution Approach 2:
The system performs automatic detection and calculation of the necessary dynamic range expansion amount without requiring user input or judgment. The detection unit and control unit work together to self-determine the optimal expansion parameters based on the actual image content, eliminating the need for user expertise in judging saturation levels.
3Reliability
If gamma correction characteristics are changed to expand dynamic range, then tone of high luminance portion can be effectively used, but unnatural image changes may occur
Solution Approach 1:
The patent applies gamma correction characteristics changes only to specific portions of the image where blown-out highlights are detected, rather than applying uniform correction to the entire image. This local application maintains natural appearance in areas that do not require correction while effectively resolving highlights in affected areas.
Solution Approach 2:
The system performs gamma correction adjustment only to the extent necessary for resolving detected blown-out highlights, rather than applying full correction globally. This partial adjustment maintains image appearance consistency in non-affected areas while effectively correcting highlight issues where they occur.
Data Source
AI summary
An image capturing apparatus includes: an image capturing unit for capturing an object image; an expander for expanding the dynamic range of the image capturing unit by reducing the exposure of the image capturing unit; a tone correction unit for performing tone correction on image data; a display unit for displaying a display image obtained by the tone correction unit; a detection unit for detecting signal values of a region within a screen of the image capturing unit after the expander expands the dynamic range; and a control unit for, in the case where the dynamic range is expanded, changing a characteristic of tone correction so as to suppress change in the display image caused by the change in the dynamic range.