Towards Spatially-Varying Gain and Binning
Journal:
arXiv
Published Date:
Jul 5, 2025
Abstract
Pixels in image sensors have progressively become smaller, driven by the goal
of producing higher-resolution imagery. However, ceteris paribus, a smaller
pixel accumulates less light, making image quality worse. This interplay of
resolution, noise, and the dynamic range of the sensor and their impact on the
eventual quality of acquired imagery is a fundamental concept in photography.
In this paper, we propose spatially-varying gain and binning to enhance the
noise performance and dynamic range of image sensors. First, we show that by
varying gain spatially to local scene brightness, the read noise can be made
negligible, and the dynamic range of a sensor is expanded by an order of
magnitude. Second, we propose a simple analysis to find a binning size that
best balances resolution and noise for a given light level; this analysis
predicts a spatially-varying binning strategy, again based on local scene
brightness, to effectively increase the overall signal-to-noise ratio. %
without sacrificing resolution. We discuss analog and digital binning modes
and, perhaps surprisingly, show that digital binning outperforms its analog
counterparts when a larger gain is allowed. Finally, we demonstrate that
combining spatially-varying gain and binning in various applications, including
high dynamic range imaging, vignetting, and lens distortion.
