Image Capturing Apparatus Exposure Control for Hue Shift Prevention
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Solution Overview
Problem
Adaptive gray level correction in image capturing can cause hue shift, leading to undesirable color changes in images, such as a blue sky becoming unclear and flowers turning yellowish, when the exposure value is set lower than the appropriate exposure value.
Innovation Solution
An image capturing apparatus with exposure control and adjustment means that calculates a correct exposure value and adjusts the exposure compensation based on conditions like high chroma, saturation, and presence of blue sky images to prevent hue shift by reducing the underexposure value and correction amount.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If adaptive gray level correction is performed on image data captured with underexposure to correct brightness and contrast, then image brightness and contrast are improved, but hue shift occurs causing color distortion
Solution Approach 1:
The patent changes the exposure value parameter from a fixed underexposure setting to a dynamically adjusted value based on detected image conditions. When blue sky or high-chroma regions are detected, the exposure value is increased to prevent hue shift, while maintaining underexposure for other scenes to preserve dynamic range and prevent overexposure in highlights.
Solution Approach 2:
The patent implements feedback by detecting image characteristics (blue sky presence, chroma values, saturation levels) after capture and using this information to adjust the exposure value for subsequent corrections. This closed-loop approach prevents hue shift by adapting the exposure setting based on actual image content analysis.
2Reliability
If exposure value is set lower than correct exposure value to prevent overexposure in highlights, then highlight detail is preserved, but image becomes underexposed and requires correction
Solution Approach 1:
The patent applies local quality by treating different regions of the image differently. It preserves underexposure for regions that need dynamic range (to prevent highlight overexposure) while applying selective exposure adjustment to specific regions like blue sky or high-chroma areas to prevent hue shift. This allows simultaneous preservation of highlight detail and prevention of color distortion in critical areas.
Data Source
AI summary
In an image capturing apparatus, a hue shift is prevented. A digital camera has a gray level correction function. Image data obtained with a CCD 10 is divided into a plurality of blocks and further has brightness data and color difference data converted in a brightness/color difference conversion section 20. When it is determined, based on the color difference data, that image data includes blue sky image or that chroma of the image data is high, an image processing exposure compensation adjustment/exposure correction amount calculation section 30 sets an underexposure value, which is employed when capturing images with an exposure value being lower than a correct exposure value, to be smaller than a default value to prevent a hue shift caused by gray level correction performed by a gray level correction section 32.