prfile=bindgen(256,5)
c='0'
ff=bytarr(256,256)
for j=0,4 do begin
    f=string(j,form='(i1)')
    openr,u,'flat/ffimg_'+c+f+'.dat',/get
    readu,u,ff
    free_lun,u
    prfile(0,j)=ff(*,135)
    endfor
contour,prfile(170:179,*),indgen(10)+170,indgen(5)
end