Flash Color Temperature Control for Accurate Photometry
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Solution Overview
Problem
Existing image pickup apparatuses face challenges in accurately determining the main light emission amount when the emission color temperature differs between preliminary and main light emissions, especially when using light sources with spectral characteristics unlike those of standard or perfect radiators, leading to increased data requirements and calculation time, and difficulties in high-magnification, long-distance, or environmental light conditions.
Innovation Solution
An image pickup apparatus equipped with a processor that measures object luminance during preliminary light emission and adjusts the light emission ratio between different color temperature light sources, allowing for selection of appropriate emission color temperatures based on spectral characteristics, shooting conditions, and photometric values to determine the main light emission amount, either through additional preliminary emissions or using initial photometric results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If correction value calculation is performed based on color temperature difference using standard light source spectral characteristics, then calculation is simplified, but accuracy deteriorates when using nonstandard light sources like white LED
Solution Approach 1:
The patent changes the parameter of light source spectral characteristics from standard to nonstandard (white LED), which requires changing the calculation method from simple color temperature difference-based correction to detailed optical spectrum data-based correction, resolving the contradiction between calculation simplicity and accuracy
Solution Approach 2:
The patent introduces detailed optical spectrum data as an intermediary between the light source and the correction value calculation, allowing accurate correction for nonstandard light sources while maintaining a systematic calculation approach
2Measurement precision
If detailed optical spectrum data is used for correction value calculation, then accuracy is improved, but data quantity and calculation time increase
Solution Approach 1:
The patent performs preliminary light emission to measure object luminance and color temperature before main light emission, preparing the necessary data in advance to enable accurate correction value calculation without increasing main shooting time
Solution Approach 2:
The system uses its own photometry unit to automatically perform spectral measurement and correction value calculation, making the process self-contained and efficient without requiring external intervention
3Ease of operation
If preliminary light emission is performed at fixed color temperature, then device operation is simplified, but adaptability to different shooting conditions deteriorates
Solution Approach 1:
The patent makes the preliminary light emission color temperature dynamic by selecting between first and second color temperatures based on shooting conditions such as object distance, reflectivity, and environmental light, resolving the contradiction between operational simplicity and adaptability
Solution Approach 2:
The patent segments the shooting conditions into different categories (e.g., bounce shooting, long-distance, high-magnification, environmental light conditions) and assigns different preliminary light emission strategies to each segment, enabling targeted adaptation
4Loss of time
If single preliminary light emission is performed, then time consumption is reduced, but measurement precision deteriorates in challenging shooting conditions
Solution Approach 1:
The patent implements periodic preliminary light emission by performing a second preliminary light emission at a different color temperature when shooting conditions indicate potential measurement errors, balancing time consumption with measurement precision
Solution Approach 2:
The system uses feedback from shooting condition analysis (object distance, reflectivity, environmental light levels) to determine whether to perform additional preliminary light emission, ensuring accurate photometric measurements while minimizing unnecessary time consumption
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
Ensures accurate main light emission amounts without limiting the light source to standard or perfect radiator characteristics, improving calculation efficiency and accuracy across various shooting conditions.
Implementation Method 1
a flash device that can change an emission color temperature by changing a ratio of light emission between a plurality of light sources which are different in emission color temperature
Implementation Method 2
configured to measure a luminance of light reflected from an object at the time of preliminary light emission
Data Source
AI summary
An image pickup apparatus capable of ensuring the accuracy of a proper main light emission amount. A flash device can change an emission color temperature by changing a ratio of light emission between light sources different in emission color temperature. A photometry unit measures a luminance of light reflected from an object by preliminary light emission of the flash device. It is selected whether to perform second preliminary light emission at a color temperature changed according to at least one of spectral characteristics information of the light source, shooting condition information, and photometric value information obtained by first preliminary light emission, and determine a main light emission amount based on a photometric result obtained by second preliminary light emission, or to determine the main light emission amount based on a photometric result obtained by first preliminary light emission without performing second preliminary light emission.