Flash Emission Control Using Face Block Weighting
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Solution Overview
Problem
Existing flash photography techniques face challenges in controlling flash emission due to abnormal reflection light, particularly from glasses, leading to increased calculation complexity as the number of face area divisions increases.
Innovation Solution
An image pickup apparatus that calculates reflection and ambient light luminances, detects face areas, and determines flash emission amounts by weighting blocks within the face area, reducing the influence of abnormal luminance blocks and using estimation luminance ranges to optimize flash photography with reduced calculation complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the face area is divided into more blocks to reduce the influence of abnormal reflection light, then the exposure accuracy is improved, but the calculation amount increases
Solution Approach 1:
The face area is divided into multiple blocks to calculate reflection luminances separately, allowing abnormal regions (such as glasses) to be identified and excluded from the average calculation. This segmentation enables more accurate exposure determination by focusing on normal skin regions only.
Solution Approach 2:
Different weights are assigned to different blocks based on their reflection luminance characteristics. Blocks with abnormal reflection (e.g., glasses causing specular reflection) are assigned lower weights or excluded, while normal skin blocks receive higher weights. This local quality differentiation improves accuracy without requiring all blocks to be processed equally.
2Manufacturing precision
If the face area is divided into finer blocks to exclude abnormal reflection regions, then the flash emission control accuracy is improved, but the processing complexity increases
Solution Approach 1:
The system changes the parameter of block weight dynamically based on reflection luminance values. Blocks with reflection luminance outside the expected range (indicating abnormal reflection from glasses) are assigned reduced weights. This parameter change approach allows the system to adapt to different shooting conditions without increasing structural complexity.
Data Source
AI summary
An image pickup apparatus that is capable of reducing influence of abnormal reflection light at pre-emission upon determination of an emission amount for main photographing. The image pickup apparatus calculates reflection luminances of reflected light from an object at pre-emission of a lighting device, detects a face area from an image, divides the face area into blocks, calculates a face reflection luminance from a weighted average of reflection luminances of the blocks and first weights of the blocks, calculates a face ambient light luminance from a weighted average of ambient light luminances of the object of the blocks and second weights of the blocks, and determines an emission amount of the lighting device for main photographing with using the face reflection luminance and the ambient light luminance. A first weight of an abnormal luminance block is reduced than that of a block other than the abnormal luminance block.