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Volume: 29 | Article ID: art00002
Measuring MTF with wedges: pitfalls and best practices
  DOI :  10.2352/ISSN.2470-1173.2017.19.AVM-451  Published OnlineJanuary 2017

As digital imaging becomes more widespread in a variety of industries, new standards for measuring resolution and sharpness are being developed. Some differ significantly from ISO 12233:2014 Modulation Transfer Function (MTF) measurements. We focus on the ISO 16505 standard for automotive Camera Monitor Systems, which uses high contrast hyperbolic wedges instead of slantededges to measure system resolution, defined as MTF10 (the spatial frequency where MTF = 10% of its low frequency value). Wedges were chosen based on the claim that slanted-edges are sensitive to signal processing. While this is indeed the case, we have found that wedges are also highly sensitive and present a number of measurement challenges: Sub-pixel location variations cause unavoidable inconsistencies; wedge saturation makes results more stable at the expense of accuracy; MTF10 can be boosted by sharpening, noise, and other artifacts, and may never be reached. Poor quality images can exhibit high MTF10. We show that the onset of aliasing is a more stable performance indicator, and we discuss methods of getting the most accurate results from wedges as well as misunderstandings about low contrast slanted-edges, which correlate better with system performance and are more representative of objects of interest in automotive and security imaging.

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Norman Koren, Robert C Sumner, Henry Koren, "Measuring MTF with wedges: pitfalls and best practicesin Proc. IS&T Int’l. Symp. on Electronic Imaging: Autonomous Vehicles and Machines,  2017,  pp 6 - 11,

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