Camera Exposure Control for Highlight Gradation and Shadow Detail
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Solution Overview
Problem
Conventional exposure control methods in digital cameras often result in loss of gradation in high luminance or low luminance regions when dealing with scenes containing both, and highlight photometry fails to provide fine adjustments, leading to underexposure in important regions.
Innovation Solution
An image pickup apparatus with sensors and processors that calculate overall and high/low luminance values, determining target exposure based on user-set thresholds to maintain appropriate gradation in high luminance regions while preventing underexposure in low luminance areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional exposure control calculates average luminance of the whole image, then exposure is appropriate for scenes with small luminance difference, but exposure shifts occur and gradation is lost in scenes with both high and low luminance regions
Solution Approach 1:
The image region is segmented into high luminance regions and low luminance regions based on a predetermined threshold. Exposure control is then performed separately for each region type, allowing the high luminance region to maintain gradation while the low luminance region avoids underexposure, resolving the contradiction between overall exposure accuracy and local gradation preservation.
2Measurement precision
If highlight photometry performs intensive photometry on high luminance region, then gradation in high luminance region is improved, but fine adjustment cannot be performed and brightness in other important regions drops too low
Solution Approach 1:
Different exposure control strategies are applied to different regions: intensive photometry is applied to high luminance regions to preserve gradation, while average luminance photometry is applied to low luminance regions to maintain adequate brightness. This local differentiation resolves the contradiction between improving high luminance gradation and maintaining brightness in other regions.
3Reliability
If exposure control focuses on high luminance object, then gradation in high luminance region is maintained, but underexposure occurs excessively in other object regions
Solution Approach 1:
The photometry mode is made dynamic and adaptive based on scene characteristics. The determination unit automatically identifies whether the scene contains high luminance regions and switches between highlight photometry mode (when high luminance regions are present) and average photometry mode (when they are not present). This dynamic adaptation resolves the contradiction between maintaining gradation in high luminance regions and preventing underexposure in other regions.
Data Source
AI summary
An apparatus includes a sensor configured to pick up images, a setting device configured to set a photometry mode, and at least one processor and a memory storing instructions that cause the processor to function as a first calculation unit configured to calculate a first value from a whole of a region of an image, a second calculation unit configured to calculate a second value from, out of the region, a region whose value is a predetermined threshold or more, and a determination unit configured to determine a target value, wherein the determination unit uses the first value to determine the target value in a case where a first mode is set by the setting device, and uses the second value to determine the target value in a case where a second mode is set.