The blackening behavior of spectral lines emitted by a hollow cathode in the case of copper was further investigated at closer gas pressure intervals (259, 289, 314, 342, 375 and 416 Pa) and electrode distances (15.0, 17.5, 20.0, 22.5, 25.0, 27.5, 30.0, and 33.0 mm). Results show that a pressure range from 300 to 380 Pa can be considered a transition region in which the electrode distance corresponding to blackening maximum shifts progressively from 20 to 33 mm. These data agree with previous findings on the dependene of photographic blackening of copper spectral lines on electrode distance.