Exposure Control Stabilizing Face Detection Chattering
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Solution Overview
Problem
Image pickup apparatuses face exposure instability when switching between face evaluative photometry and center-weighted average photometry, particularly due to delayed face detection and objects cutting across the screen, leading to incorrect exposure, especially in scenes with multiple subjects.
Innovation Solution
An exposure control apparatus that includes a detection unit, a selection unit, a first judgment unit, and a second judgment unit to stabilize exposure by selecting and locking photometric modes based on consistent detection results, preventing false detection and object interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If face detection is performed to switch photometric modes, then exposure accuracy for face subjects is improved, but exposure instability occurs due to detection chattering and delayed detection
Solution Approach 1:
The system performs preliminary face detection and tracks detection states over time before committing to a photometric mode switch. By accumulating detection results over a predetermined period and requiring a threshold number of detections, the system prepares in advance to avoid premature mode switching due to transient or false detections, thereby maintaining exposure stability while still achieving accurate face exposure when conditions are met.
Solution Approach 2:
The system continuously monitors face detection results and uses this feedback to determine whether to switch photometric modes. By referring to multiple detection results and comparing them against predetermined criteria, the system creates a feedback loop that filters out false detections and ensures stable exposure control before transitioning between photometric modes.
2Stability of the object's composition
If multiple face detection results are referred to prevent detection chattering, then detection stability is improved, but detection delay increases when objects cut across the screen
Solution Approach 1:
The system dynamically adjusts its detection evaluation based on the current detection state. When a face is newly detected, the system accumulates detection results over time to confirm stability. However, when an object cuts across the screen, the system can quickly adapt by evaluating the temporal pattern of detection results, allowing it to respond more rapidly to genuine changes while still filtering out transient false detections.
Solution Approach 2:
The system requires a predetermined number of face detection results within a time period before confirming a detection state, which is a form of partial action threshold. This threshold mechanism balances the need for stability with the need for timely response, as it doesn't require excessive confirmation for every detection event but rather a reasonable number that filters false positives without causing excessive delay.
3Measurement precision
If photometric mode switching is performed based on face detection, then exposure accuracy for detected faces is improved, but incorrect exposure occurs when objects are misidentified as faces
Solution Approach 1:
The system uses feedback from multiple face detection results to verify detection reliability before switching photometric modes. By requiring a predetermined number of consistent detection results within a time period, the system filters out false detections such as objects that briefly resemble faces, thereby maintaining detection reliability while still achieving accurate exposure for genuine face subjects.
Solution Approach 2:
The system performs preliminary verification of face detection results before committing to photometric mode switching. By accumulating and evaluating multiple detection results in advance, the system ensures that only reliable face detections trigger mode changes, preventing incorrect exposure control due to false identification of objects as faces.
Data Source
AI summary
An exposure control apparatus prevents exposure from being influenced by false detection and instability of face detection and prevents exposure from being influenced by an object that has cut across in front of a subject. Detection results are obtained by detecting at least one specific region, which is predetermined in advance, in a taken image of the subject. When at least one specific region is detected, one of detection results is selected based on selecting conditions determined in advance to obtain a selected detection result. When it is judged that exposure is not being controlled using the selected detection result, whether or not the selected detection result has changed in a predetermined period is judged. When the selected detection result has not changed, a latest detection result is regarded as the selected detection result, and when the selected detection result has changed, the selected detection result is not changed.