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However, the CTF reflects only the maximum usable signal, neglecting the effects of finite electron fluence and the Poisson-limited nature of detection. As a result, it can significantly overestimate practical performance, especially in low-dose regimes. Here, we employ the spectral signal-to-noise ratio (SSNR), as a finite-dose statistical framework to evaluate the recoverable signal as a function of spatial frequency. Using numerical reconstructions of white-noise objects, we show that center-of-mass, parallax, and direct ptychography exhibit dose-independent SSNRs, with close-form analytic expressions. In contrast, iterative ptychography exhibits a surprising dose dependence: at low fluence, its SSNR converges to that of direct ptychography; at high fluence, it saturates at a value consistent with the maximum detective quantum efficiency predicted by recent quantum Fisher information bounds. The results highlight the limitations of CTF-based evaluation and motivate SSNR as a more accurate, finite-dose metric for assessing STEM phase retrieval methods.<\/jats:p>","DOI":"10.1093\/mam\/ozag005","type":"journal-article","created":{"date-parts":[[2026,1,13]],"date-time":"2026-01-13T12:30:37Z","timestamp":1768307437000},"source":"Crossref","is-referenced-by-count":7,"title":["Beyond Contrast Transfer: Spectral SNR as a Finite-Dose Metric for STEM Phase Retrieval"],"prefix":"10.1093","volume":"32","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8338-3323","authenticated-orcid":false,"given":"Georgios","family":"Varnavides","sequence":"first","affiliation":[{"name":"Miller Institute for Basic Research in Science, University of California Berkeley , Stanley Hall, Berkeley, CA 94720 ,","place":["USA"]},{"name":"National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory , 67 Cyclotron Rd, Berkeley, CA 94720 ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7591-0928","authenticated-orcid":false,"given":"Julie Marie","family":"Bekkevold","sequence":"additional","affiliation":[{"name":"School of Physics, Trinity College Dublin , College Green, Dublin D02 PN40 ,","place":["Ireland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7117-066X","authenticated-orcid":false,"given":"Stephanie M","family":"Ribet","sequence":"additional","affiliation":[{"name":"National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory , 67 Cyclotron Rd, Berkeley, CA 94720 ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6077-4698","authenticated-orcid":false,"given":"Arthur R C","family":"McCray","sequence":"additional","affiliation":[{"name":"Department of Materials Science and Engineering, Stanford University , 475 Via Ortega, Stanford, CA 94305 ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9543-6725","authenticated-orcid":false,"given":"Mary C","family":"Scott","sequence":"additional","affiliation":[{"name":"National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory , 67 Cyclotron Rd, Berkeley, CA 94720 ,","place":["USA"]},{"name":"Department of Materials Science and Engineering, University of California Berkeley , 2607 Hearst Ave, Berkeley, CA 94720 ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6907-0731","authenticated-orcid":false,"given":"Lewys","family":"Jones","sequence":"additional","affiliation":[{"name":"School of Physics, Trinity College Dublin , College Green, Dublin D02 PN40 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