Camera System Performance Derived from Natural Scenes

Oliver Van Zwanenberg,Alexandra Psarrou,Robin Jenkin,Sophie Triantaphillidou

doi:10.2352/issn.2470-1173.2020.9.iqsp-241

Abstract

The Modulation Transfer Function (MTF) is a wellestablished measure of camera system performance, commonly employed to characterize optical and image capture systems. It is a measure based on Linear System Theory; thus, its use relies on the assumption that the system is linear and stationary. This is not the case with modern-day camera systems that incorporate non-linear image signal processes (ISP) to improve the output image. Nonlinearities result in variations in camera system performance, which are dependent upon the specific input signals. This paper discusses the development of a novel framework, designed to acquire MTFs directly from images of natural complex scenes, thus making the use of traditional test charts with set patterns redundant. The framework is based on extraction, characterization and classification of edges found within images of natural scenes. Scene derived performance measures aim to characterize non-linear image processes incorporated in modern cameras more faithfully. Further, they can produce ‘live’ performance measures, acquired directly from camera feeds.

Highlights

Ever since the transition from analog to digital imaging, the camera system has increasingly becoming more complex
Unlike the traditional method of obtaining the Spatial Frequency Response (SFR), the input edges from captured natural scenes are not ‘perfect’
Due to the selected focal length, aperture and focal distances, image information was all in focus, blur resulting from shallow depth of fields was not an issue

Summary

Introduction

Ever since the transition from analog to digital imaging, the camera system has increasingly becoming more complex. Scene derived performance measures aim to characterize non-linear image processes incorporated in modern cameras more faithfully. In this paper we describe a novel framework, developed to measure the SFR from natural scene images through the adaptation of the standardized slanted edge method, ISO 12233 [4].

Results

Conclusion