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J Struct Biol. 2015 Nov;192(2):216-21. doi: 10.1016/j.jsb.2015.08.008. Epub 2015 Aug 13.

CTFFIND4: Fast and accurate defocus estimation from electron micrographs.

Author information

1
Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA.
2
Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA. Electronic address: niko@grigorieff.org.

Abstract

CTFFIND is a widely-used program for the estimation of objective lens defocus parameters from transmission electron micrographs. Defocus parameters are estimated by fitting a model of the microscope's contrast transfer function (CTF) to an image's amplitude spectrum. Here we describe modifications to the algorithm which make it significantly faster and more suitable for use with images collected using modern technologies such as dose fractionation and phase plates. We show that this new version preserves the accuracy of the original algorithm while allowing for higher throughput. We also describe a measure of the quality of the fit as a function of spatial frequency and suggest this can be used to define the highest resolution at which CTF oscillations were successfully modeled.

KEYWORDS:

Astigmatism; CTF; Defocus; Phase plate

PMID:
26278980
DOI:
10.1016/j.jsb.2015.08.008
[Indexed for MEDLINE]

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