HDR Exposure Control Using Luminance Zone Prioritization
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Solution Overview
Problem
Conventional image capture systems face challenges in accurately determining exposure conditions for high dynamic range (HDR) compositing, especially in compact cameras without an AE sensor, leading to potential picture quality degradation and increased release time lag due to manual or inaccurate exposure setting methods.
Innovation Solution
An image capture apparatus and method that computes HDR standard exposure and scene dynamic range based on subject luminance and luminance distribution information, allowing for precise determination of exposure ranges for HDR shooting, reducing the need for multiple exposure measurements and shortening the release time lag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple images are captured with different exposure amounts to achieve HDR compositing, then the dynamic range of the image is expanded, but the release time lag increases due to multiple exposure measurements
Solution Approach 1:
The patent applies preliminary action by capturing a standard exposure image first, then using that image to determine the exposure range for subsequent under-exposure and over-exposure images. This sequential approach with predetermined exposure steps eliminates the need for iterative measurements, significantly reducing release time lag while maintaining accurate HDR exposure conditions.
2Loss of time
If the exposure range is determined based on estimated values from standard exposure images, then the release time lag is reduced, but the accuracy of exposure determination decreases
Solution Approach 1:
The patent implements feedback by capturing actual under-exposure and over-exposure images and using their luminance information to verify and adjust the exposure range determination. This feedback loop ensures that the estimated exposure range from standard exposure images is corrected based on actual captured image characteristics, maintaining high accuracy while keeping the process efficient.
3Measurement precision
If an AE sensor is added to accurately measure scene dynamic range, then exposure determination accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies self-service by enabling the image capture apparatus to determine its own exposure conditions using the luminance information from images captured by its existing image sensor. The system uses the standard exposure image and subsequent under/over exposure images to self-determine the exposure range, eliminating the need for separate AE sensors or external measurement devices.
4Reliability
If the exposure amount is set too high for scenes with narrow dynamic range, then picture quality degradation occurs due to S/N deterioration, but manual exposure selection is time-consuming
Solution Approach 1:
The patent implements automatic exposure range determination by having the system itself analyze the luminance distribution of captured images to determine the appropriate exposure range. This self-determination eliminates manual exposure selection, providing both optimal picture quality through precise exposure control and ease of operation through automation.
Data Source
AI summary
An image capture apparatus is provided that is capable of accurately determining exposure conditions of multiple images to be used in high dynamic range compositing in a short duration, based on a captured image. A scene dynamic range is computed based on luminance information obtained from an image captured with a standard exposure according to a luminance zone to be prioritized in high dynamic range shooting and luminance information obtained from an image captured with an over-exposure or an under-exposure relative to the standard exposure. An exposure range of multiple images for creating a high dynamic range image is determined according to the computed dynamic range.