function lsf = WestLSFMinutes(distance)
%WESTLSFMINUTES Compute Westheimer estimate of human LSF
% lsf = WestLSFMinutes(distance)
%
% Compute Westheimer's LSF function as a function
% of passed distance. Distance passed in minutes of arc.
%
% Formula from Westheimer G. 1986. The eye as an optical instrument. In
% Handbook of perception and human performance, KR Boff, L Kaufman,
% JP Thomas (eds). New York: Wiley. Equation 8.
%
% This is only approximately consistent with Westheimer's PSF estimate.
%
% This comes back normalized to a maximum of 1.
%
% See also WestPSFMinutes, DavilaGeislerPSFMinutes, LsfToPsf, PsfToLsf
% 9/4/97 dhb Wrote it.
lsf = 0.47*exp(-3.3*(distance.^2)) + ...
0.53*exp(-0.93*(abs(distance)));