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. Author manuscript; available in PMC: 2015 May 1.
Published in final edited form as: Ultramicroscopy. 2014 Feb 7;140:9–19. doi: 10.1016/j.ultramic.2014.01.009

Table 1.

Maximum reciprocal space extent of the CTF that can be represented in a discretized form within a finite window, as computed using Eqs. (9) and (10). The entries of the table designate, for a given combination of defocus, pixel size, and window size, a fraction of the reciprocal space within which CTF is properly discretized, i.e., free of aliasing artifacts. The remaining parameters are: voltage 300 kV and the spherical aberration constant 2.0 mm. Thus, given pixel size 0.8 Å, defocus 1.5 μm, and window size 128 pixels, the fraction of reciprocal space is 0.3, i.e., the artifact-free extent of the CTF is 0.3 × 128=38 Fourier pixels. It also means that even though in this case the maximum resolution (corresponding to Nyquist frequency) is 2 × 0.8 Å=1.6 Å, the actual maximum resolution that can be recovered from the data is only 1.6/0.3=5.3 Å.

Window size Defocus
0.8 μm 1.0 μm 1.5 μm 2.5 μm
Pixel size 0.8 Å 64 0.3 0.2 0.2 0.1
128 0.6 0.5 0.3 0.2
256 1.0 1.0 0.6 0.3
512 1.0 1.0 1.0 0.7
Pixel size 1.0 Å 64 0.5 0.3 0.2 0.2
128 1.0 0.8 0.5 0.3
256 1.0 1.0 1.0 0.5
512 1.0 1.0 1.0 1.0
Pixel size 1.4 Å 64 1.0 0.8 0.5 0.3
128 1.0 1.0 0.9 0.5
256 1.0 1.0 1.0 1.0
512 1.0 1.0 1.0 1.0