The new slimline Darren Clarke stayed within touching distance of the leaders after another impressive round in the Volvo Golf Champions at Durban Country Club
Clarke, who won the Open at Royal St George's in 2011 but has failed to record a single top-10 finish on the European Tour in the last two years, was just two shots off the lead after the first round following a three-under par 69.
And he continued that fine form yesterday when he again recorded an under par round.
The Ulsterman got off to a flying start as he birdied three of his first four holes, but he faltered later on and eventually had to settle for a 71.
A spectacular albatross helped Dutchman Luiten claim a share of the lead at the halfway stage.
He holed his second shot to the 560-yard 10th from 248 yards, his four-iron approach pitching just short of the green and running 20 yards up the green and into the hole.
The 28-year-old, who celebrated his birthday on Tuesday, eventually carded a second round of 67.
"It's my first albatross," said Luiten, who is just outside the automatic Ryder Cup qualifying places after winning the KLM Open in his home country last year.
"I hit a good drive down the middle of the fairway, 227 metres left, hit a four iron and basically went straight at it.
"It pitched exactly where I wanted, just front of the green and released up the slope and straight at the pin and went in. It was a good feeling.
"I didn't really do a lot over the winter. I had three weeks off and I didn't really practice. You never know how you are going to play after that but luckily the game is still all right. The funny thing is yesterday it felt terrible but I was making some good swings today, so that gives you some trust hopefully for the coming days."
Padraig Harrington hailed the skills of his stand-in caddie after regular bagman Ronan Flood needed medical treatment during the second round of the tournament.
Flood, who is also Harrington's brother-in-law, was suffering from food poisoning before the round and eventually had to call it quits on the sixth hole.
He was taken to the clubhouse to be treated by a doctor and is expected to be fit to resume his duties today, although stand-in caddie Pat Cashman has again offered his services if required.
Cashman, 65, is a photographer for the Golfing Union of Ireland who has known Harrington for 35 years and was in the gallery following his fellow Irishman while in South Africa on holiday.
Harrington, who carded a second consecutive 71 to finish two under par, said: "Ronan felt like he needed to throw up and as he went out on the course he thought it would clear a bit but it got worse and worse and for him to give up....I don't think I have ever seen him do that in any circumstances.
"He felt like he was getting in the way and when we finally said goodbye he could not physically stand up. I really did feel bad because he was lying there but thankfully there was a friend of ours out there who holidays down here and he took over.
"He started off like he was carrying bows and arrows but by the end he had the double-strap going (on the bag) and was using all the lingo.
"It's amazing how much caddies do for you and it gives you a new appreciation for what they do out there. I know now why we pay them the big bucks!"
Cashman, who has never caddied before but is a member with Flood at the Heritage in Ireland, said: "The bag was lighter than I expected. It was very comfortable.
"I saw Ronan on the range and he looked awful. I said if you need help, call me. They sent out a replacement caddie but Padraig asked if I would be happy to continue and I was. I told him I wouldn't give him a line or a club but he was so easy to work for.
"I've given him my phone number if he needs me but hopefully Ronan will be okay."