The electron distribution of open-ended single-walled carbon nanotubes (CNTs) with chirality indexes (7,0) and (5,5) in field emission conditions was calculated via a multi-scaled algorithm. The field emission images were produced numerically. It was found that the emission patterns change with the applied macroscopic field. Especially, the symmetry of the emission pattern of the (7,0) carbon nanotube is breaking in the lower field but the breaking is less obvious in the higher field. The magnification factor increases with the applied macroscopic field.