Flash Photography Image Blending for Exposure Uniformity
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Solution Overview
Problem
Mobile electronic devices, such as smartphones, face challenges in capturing high-quality images in low-light conditions due to non-uniform radiance and aesthetic issues like over-exposure, under-exposure, unnatural saturation, ghosting artifacts, and bluish color casts when using flashes, and existing methods to combine images often result in noise and unnatural colors.
Innovation Solution
The method involves capturing multiple ambient and flash images using a pilot flash sequence, analyzing exposure differences to determine optimal flash strength, and blending these images to achieve uniform radiance and natural colors, thereby improving image quality in low-light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a flash is used to illuminate the scene, then the subject is brightly lit, but the background becomes under-exposed and non-uniform radiance is created
Solution Approach 1:
The patent segments the imaging process into multiple captures: ambient light images without flash and flash images with varying exposure settings. By separating these captures and processing them independently, the system can optimize subject illumination while maintaining background exposure uniformity through selective blending of regions from different captures.
Solution Approach 2:
The patent applies local quality by differentiating treatment between subject regions and background regions. Through analysis of multiple image pairs, the system determines optimal flash strength for subjects while preserving background exposure characteristics, creating non-uniform radiance patterns that are locally optimized rather than globally uniform.
2Manufacturing precision
If multiple images are combined to improve aesthetics, then exposure uniformity improves, but unnatural saturation artifacts and ghosting occur
Solution Approach 1:
The patent performs preliminary action by capturing multiple ambient images and flash images with varying exposures before final processing. These preliminary captures provide a library of reference data that guides the subsequent blending process, allowing the system to predict and avoid saturation artifacts by selecting appropriate exposure combinations in advance.
Solution Approach 2:
The system uses feedback from analyzing multiple image pairs to determine optimal flash strength and exposure settings. By continuously evaluating the relationship between ambient and flash images, the system adjusts blending parameters to eliminate unnatural saturation while maintaining exposure uniformity, creating a feedback-driven optimization process.
3Illumination intensity
If flash strength is increased to brighten the scene, then overall illumination improves, but over-exposure and bluish color casts increase
Solution Approach 1:
The patent applies parameter changes by systematically varying camera exposure settings across multiple flash image captures. By capturing images at different exposure levels and using this variation to determine optimal flash strength through analysis of image pairs, the system can brighten the overall scene while avoiding over-exposure and bluish color casts through precise parameter optimization.
Data Source
AI summary
A method includes capturing multiple ambient images of a scene using at least one camera of an electronic device and without using a flash of the electronic device. The method also includes capturing multiple flash images of the scene using the at least one camera of the electronic device and during firing of a pilot flash sequence using the flash. The method further includes analyzing multiple pairs of images to estimate exposure differences obtained using the flash, where each pair of images includes one of the ambient images and one of the flash images that are both captured using a common camera exposure and where different pairs of images are captured using different camera exposures. In addition, the method includes determining a flash strength for the scene based on the estimate of the exposure differences and firing the flash based on the determined flash strength.