Figure 2.

Optimization of the radius for the mask of the Fourier transform of image 3552. The plot shows the dependence of the final number of good spots obtained in the 200- to 3.5-Å resolution range on the radius used in the reciprocal space averaging procedure. The radius is used to mask the Fourier transform of the image (see Materials and Methods). Good spots have a signal-to-noise ratio greater than 1.0 after correction for the background. Inset shows for the indicated resolution ranges the relation between the radius and the averaged height of the image diffraction peaks above the perimeter average, scaled so that the average background has a value of 7.