Learning Lens Blur Fields

TL;DR

This paper introduces a neural representation called the lens blur field, which models complex optical blur variations across different camera settings and devices, enabling accurate characterization of lens behavior.

Contribution

We propose a high-dimensional neural model for lens blur fields and a method to learn them from focal stacks, capturing device-specific optical effects in a parametric form.

Findings

The lens blur field accurately models optical variations across image plane, focus, and depth.

The method can distinguish optical differences between similar smartphone devices.

A new dataset of 5D blur fields for various cameras is provided.

Abstract

Optical blur is an inherent property of any lens system and is challenging to model in modern cameras because of their complex optical elements. To tackle this challenge, we introduce a high-dimensional neural representation of blur$-$$\textit{the lens blur field}$$-$and a practical method for acquiring it. The lens blur field is a multilayer perceptron (MLP) designed to (1) accurately capture variations of the lens 2D point spread function over image plane location, focus setting and, optionally, depth and (2) represent these variations parametrically as a single, sensor-specific function. The representation models the combined effects of defocus, diffraction, aberration, and accounts for sensor features such as pixel color filters and pixel-specific micro-lenses. To learn the real-world blur field of a given device, we formulate a generalized non-blind deconvolution problem that directly optimizes the MLP weights using a small set of focal stacks as the only input. We also provide a first-of-its-kind dataset of 5D blur fields$-$for smartphone cameras, camera bodies equipped with a variety of lenses, etc. Lastly, we show that acquired 5D blur fields are expressive and accurate enough to reveal, for the first time, differences in optical behavior of smartphone devices of the same make and model. Code and data can be found at blur-fields.github.io.