"It felt better and more in tune with racing again, " Kean said. "Going into that race in the side lane I knew I had nothing to lose and just go out there to better myself.
"It is a bigger show tonight. There are more people in the stands and it makes everything a lot more exciting so the key is to keep yourself grounded. You just have to go down and back in a lane so you don't have to do anything else and just give it your all.''
Kean believes he has more to give for the final.
"I am always looking to go faster, there's no doubt about that. For me it will be another great competition and a fun race because you only get to race guys of this level once every couple of years and I want to make the most of it.''
Earlier Kean made a slow start to finish fifth in the final heat in 54.37.
Also in the morning heats, Boyle clocked 16:02.90 to finish third behind 2011 world champion Lotte Friis of Denmark who was the fastest qualifier for the 1500m freestyle in 15:49.26.
Boyle's time was a tick under 14 seconds faster than her New Zealand record of 16:16.83 set at the New Zealand open championships in March.
The 25-year-old set a solid schedule, not drawn into the blistering early pace of Friis who was well under the world record split in the early stages. The Kiwi went through the 400m in 4:12, the 800m in 8:30 and the 1200 in 12:48 in a controlled performance.
Friis was fastest overall, a shade ahead of yesterday's 400m gold medallist Katie Ledecky (USA) with Chilean veteran Kristel Kobrich third fastest, with the trio the only swimmers under the 16-minute barrier.
"It is not an event the girls swim very often so Lauren's entry time was the national record from the trials,'' Swimming New Zealand head coach David Lyles said. "To take 14 seconds off at any age and certainly with Lauren as being an elder swimmer, is a phenomenal effort.
"Like the 400m, she was in an early heat and had to make sure of her qualification. She was in with the world record holder in Lotte Friis and had to put her foot down. She did that and I was very pleased with it.''
Lyles is not concerned with Boyle's busy schedule for the championships.
"She has a big programme in terms of total volume but it is only three events and it is spread over eight days. Going from the 400 last night with the elation, the joy and the relief I guess for the medal to the 1500m this morning was probably the biggest test.
"She gets 30 hours recovery now and so, for someone doing 75,000m to 80,000m a week, the recovery in terms of getting ready for tomorrow night shouldn't be a problem.''
Stanley made a strong start in his heat of the 200m freestyle. He went through in 52.71s and finished fourth in his heat in 1:48.01, which was only 0.3s outside his national record.
He was handily placed at the 100m mark in the semifinal in 52.35 but tied up over the second half of the race.
In tomorrow's third morning of heats, Glenn Snyders returns for the 50m breaststroke where he is ranked fourth in the world this year, and Wellington's Samantha Lucie-Smith and North Shore's Shaun Burnett will make their world championship debuts in the 200m freestyle and 200m butterfly respectively.
Results from day two of the world swimming championships at Barcelona, Spain, today (NZT):Heats, 1500m freestyle: Lotte Friis (DEN) 15:49.18, 1; Katie Ledecky (USA) 15:49.26, 2; Kristel Kobrich Schimpl (CHI) 15:54.30, 3. Also: Lauren Boyle (NZL) 16:02.58, 6 (NZ Record).
Semifinal qualifiers, men 200m backstroke: Matt Grevers (USA) 52.97, 1; David Plummer (USA) 53.10, 2; Jeremy Stravius (FRA) 53.23, 3. Also: Gareth Kean (NZL) 53.81, 8.
Semifinal qualifiers men 200m freestyle semifinal: Danila Izotov (RUS) 1:45.84, 1; Ryan Lochte (USA) 1:46.06, 2; Kosuke Hagino (JPN) 1:46.87, 3. Also: Matthew Stanley (NZL) 1:48.35, 16.
