Grey Card with Focus Target for Camera Exposure Calibration
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Solution Overview
Problem
Existing methods for setting exposure and white balance in digital cameras, such as using grey cards, can be time-consuming and confusing for amateur photographers, especially when the scene's light reflectance differs significantly from the assumed 18% value, leading to exposure issues like underexposure in scenes with large expanses of snow and sky.
Innovation Solution
A target with a 18% reflectance surface and a distinct feature for camera focus is used to automatically set exposure and white balance by positioning it close to the subject, allowing the camera to focus and adjust settings before taking a photograph, then removing the target while maintaining the settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a grey card with 18% reflectance is used to set exposure, then exposure accuracy is improved, but the process becomes time-consuming and confusing for amateur photographers
Solution Approach 1:
The patent combines the grey card functionality with a focus target feature into a single integrated card. The card includes a grey surface with 18% reflectance for exposure calibration and a distinct focus target (such as a black circle or pattern) that enables automatic focusing. This merging allows the photographer to perform exposure and focus calibration in a single step, eliminating the need for separate operations and reducing the overall time required while maintaining accuracy.
Solution Approach 2:
The card serves multiple functions simultaneously: it acts as a grey card for exposure calibration, a focus target for automatic focusing, and a white balance reference. By making the card multi-functional, the patent reduces the number of separate tools and steps needed, making the process faster and less confusing for amateur photographers while preserving the accuracy benefits of each individual function.
2Measurement precision
If manual exposure adjustment is used, then exposure accuracy can be improved, but the ease of operation decreases for amateur photographers
Solution Approach 1:
The camera system performs self-service by automatically adjusting exposure and white balance settings based on the reflected light from the grey card. The light meter detects the 18% reflectance of the grey surface, and the microprocessor automatically calculates and applies the appropriate exposure compensation and white balance settings. This eliminates the need for manual adjustment while maintaining accuracy, making the camera easier to operate for amateur photographers.
3Ease of operation
If automatic exposure mode is used, then ease of operation is improved, but exposure accuracy deteriorates when scene reflectance differs from 18%
Solution Approach 1:
The patent applies preliminary action by using the grey card with 18% reflectance to pre-calibrate the camera's exposure and white balance settings before photographing the actual scene. The camera measures the reflected light from the grey card and automatically adjusts its parameters accordingly. This preliminary calibration ensures that when the photographer switches to automatic mode for the actual shot, the camera already has accurate exposure settings, resolving the inaccuracy that would otherwise occur when scene reflectance differs from the assumed 18% value.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows amateur photographers to quickly and easily set camera exposure and white balance automatically, ensuring accurate settings without the need for manual adjustments, making the process simpler and more efficient.
Implementation Method 1
a target surface that has a reflectance of 18% for all wavelengths of visible light
Data Source
AI summary
A target (10, 20) is disclosed suitable for setting the exposure and white balance of a photographic digital camera. The target (10, 20) comprises a target surface (12) that has a reflectance of 18% for all wavelengths of visible light. The target surface (12) is provided with a feature (16) upon which the camera is able to focus.