. Author manuscript; available in PMC: 2015 Jul 9.

Published in final edited form as: J Struct Biol. 2013 Feb 11;182(2):93–105. doi: 10.1016/j.jsb.2013.01.011

Table 1.

Signal-to-noise ratios at different resolutions. The Signal-to-noise ratio is defined as ratio between the variances of the signal and the noise.

Resolution (Å)	7.2	30	30
Measurement Area (Pixels)	25,600	25,600	7,825
SNR=∞	∞	∞	∞
SNR=1	0.035	1	8.821
SNR=0.25	0.009	0.25	0.551
SNR=0.1	0.004	0.1	0.088

First column: With Pixel size of 3.6Å and the full resolution of 7.2Å (Nyquist-Shannon), using the full image (160×160). Second column: the SNR after low-pass filter to 30Å, Third column: at 30Å resolution with the image area restricted closer to the signal area (mask radius 50). Since the noise covers all frequencies, low-pass filtering to 30Å results in a higher signal-to-noise ratio.