mVm f 2nm^rnaxV ^
Here MTF(0) is just the sum done for v = 0, and m is the summation index. EE(ymca) is the fractional encircled energy as far as the point-spread function integral is done. Nf is the number of angles in the intensity summation. The effect on the MTF is to induce a small downward curl at low spatial frequencies. In most of the figures appearing in this book, the intensity function was carried out to angles where the lower part of the MTF could be approximated by a straight line to the known intercept of unity at the origin. Usually, the encircled energy at the most distant angle of a focused pattern exceeded 99%.
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