Analysis of Natural Scene Derived Spatial Frequency Responses for Estimating Camera ISO12233 Slanted-edge Performance

Abstract

The Natural Scene derived Spatial Frequency Response (NS-SFR) framework automatically extracts suitable step-edges from natural pictorial scenes and processes these edges via the edge-based ISO12233 (e-SFR) algorithm. Previously, a novel methodology was presented to estimate the standard e-SFR from NS-SFR data. This paper implements this method using diverse natural scene image datasets from three characterized camera systems. Quantitative analysis was carried out on the system e-SFR estimates to validate accuracy of the method. Both linear and non-linear camera systems were evaluated. To investigate how scene content and dataset size affect system e-SFR estimates, analysis was conducted on entire datasets, as well as subsets of various sizes and scene group types. Results demonstrate that system e-SFR estimates strongly correlate with results from test chart inputs, with accuracy comparable to that of the ISO12233. Further work toward improving and fine-tuning the proposed methodology for practical implementation is discussed.

Estimation of ISO12233 Edge Spatial Frequency Response from Natural Scene Derived Step-Edge Data

“…When implementing the method on a dataset captured with a highly non-linear system, the results are not comparable with an edge test chart [4,17]. But this is expected, as the non-linear ISP sharpens isolated chart edges, whilst natural scene edges generally are not as sharpened due to surrounding textures and denoising.…”

“…Further qualitative analysis of the results from the implementation can be found in Ref. [4] by the same authors.…”

“…These observations indicate that the NS-SFRs can potentially form a scene dependent performance measure. Splitting the dataset up per scene category indicates that the system e-SFR estimate has a scene-dependent nature [4].…”

“…Detailed system e-SFR results from the two DSLR camera systems and a smartphone camera system are presented in Ref. [4] by the same authors.…”

“…The study provides insights for setting parameter ranges to obtain stable system e-SFR estimates. The methodology for estimating the system e-SFR is discussed, followed by an overview of estimate validation; a complete analysis of the results is presented in [4] by the same authors. The paper concludes by discussing advantages and improvements to the current version of the framework and further work required for real-time implementation.…”