function calc_spd, psf

iminfo,psf,dim,npsf
dim=dim(0)

fto= psf*0.

for i=0,npsf-1 do begin
    fto(*, *, i)=abs(eclat(fft(eclat(psf(*, *, i)), -1)))
    fto(*, *, i)=fto(*, *, i)/max(fto(*, *, i))
endfor
spd=total(fto^2, 3)/npsf -abs(total(fto, 3)/npsf)^2
spd1D=(circmoy(spd,/milieu))

spdo=fltarr(dim, dim)

for i=0,fix(dim/sqrt(2.)) do begin
    selectfreq=eclat(distc(dim))
    selectfreq=(selectfreq lt (i+1)) and (selectfreq ge (i))
    spdo(where(selectfreq eq 1))=spd1D(i)
endfor

return,spdo

end