 To accommodate a 4-way prism splitter, extra distance was needed, from the back of the lens to the image focal plane, when compared to a 3-tube splitter.This set severe demands for the lens designer, but Angenieux were able to achieve EMI's requirements, provided that field flattening lenses were fitted in front of each pick-up tube.Early cameras used this arrangement, but with later zoom designs these lenses became unnecessary.