Previous days in this Test ended early because of bad light
Umpire Simon Taufel insisted the right decision was made in offering the light to South Africa after the second Test against England ended in a draw.
England were two wickets away from victory when play was called off on the final day 15 overs early.
"It's unfortunate for cricket but we tried to be consistent with what we did earlier in the match," Taufel said.
"It was agreed by both captains that once artificial lighting was used we weren't playing normal cricket."
The floodlights had been on for several overs when Taufel and fellow umpire Darrell Hair gave AB de Villiers and Makhaya Ntini the option to leave the field.
"We discussed these issues before the series," Taufel added.
"Once we consider the light unfit for play we offer it to the batsmen."
Taufel was asked whether the match could have continued if England had chosen to bowl spinners instead of paceman Steve Harmison.
"That's hypothetical. I don't remember what the light was at that time," he answered.