This is Seresin's first "native" 3D movie, after his work on Gravity, which was converted to 3D in the post-production process.
Talking to TimeOut from London, Seresin agrees that the film's misty forest scenes retrospectively prove his suggestion before the shoot that the film could have been shot in New Zealand.
But from his offices in Seatoun, Letteri's chuckles are reserved for the film's unknowing extras -- the chimpanzees of Wellington Zoo.
It seems that Marty, Sally, Beni, Bakari, Malika and the rest of the zoo's 13 chimps will, should they ever get to see the new film, be able to recognise themselves on screen.
"We've got a great relationship with the Wellington Zoo," says Letteri on a break from supervising the visual effects on the final Hobbit film.
"And if you go to the zoo, you'll notice that some of the chimps that you see in the enclosure look very similar to the chimps on the screen."
Weta's animators made digital replicas of the troop to help populate the movie's vast colony.
"They have great personalities and we just thought 'we need background apes. Why not use these guys?'".
Watch: Weta Digital's groundbreaking apes
Dawn of the Planet of the Apes needed more chimps and more digital capacity for a reason. They also needed to be shot outdoors, at the insistence of the movie's director Matt Reeves, which meant a whole new set of challenges for Weta Digital, which is co-owned by Letteri, a four-time visual effects Oscar winner since joining Weta on the second Lord of the Rings movie and becoming partners with Peter Jackson in the company.
The story takes place 10 years after the previous one.
That ended with Caesar emerging from a San Francisco lab -- and home schooling by James Franco's scientist -- as a super-intelligent primate and clear alpha male to his fellow ape captives. Since then, the "Simian Virus" concocted in the same lab has decimated much of the human race. Among the few San Franciscan survivors holed up in an electricity-free but heavily armed ghetto are characters played by Gary Oldman, Jason Clarke, and Keri Russell.
Events bring the city human colony and the forest ape colony into conflict with Caesar and Clarke's character trying to prevent all-out inter-species warfare.
In 2011 Rise of the Planet of the Apes became a surprise hit, grossing nearly US$500 million worldwide with a budget of about US$93 million. The surprise was that Dawn was a reboot of The Planet of the Apes franchise which had already failed to fire with Tim Burton's 2001 offbeat remake.
The original Planet of the Apes movie of 1968 had spawned four sequels and the 1974 television series, with heavily made-up actors like Roddy McDowall, Maurice Evans and Kim Hunter in the lead primate roles.
The new movie, which has an estimated US$120 million budget, follows the origin story of Rise, in a continuing narrative which could eventually connect to the events of the original film.
Like Rise is also pays homage to the earlier movies -- a wise orangutang character is called "Maurice" after the man who played Dr Zaius.
For Weta Digital, the apes may be much smaller than their Kong but there are many more of them.
Watch: Trailer: Dawn of the Planet of the Apes
Letteri estimates work on Dawn used 10 times more computer processing power than the 2005 Peter Jackson movie.
But the biggest technical difference on this one was taking the motion-capture process ("mo-cap") on location. That meant taking the actors in the sensor suits out of a studio environment and into Canadian forests (substituting for the story's Northern California setting) or New Orleans, substituting for a post-apocalyptic downtown San Francisco.
The locations meant a Weta team had to figure out how it could be done in rainy, muddy conditions not ideal for delicate electronics.
In British Columbia, that meant rigging specially developed wireless motion capture cameras in the trees and wherever they could to cover a scene -- one which was also being shot in 3D by Seresin and his crew at the same time -- then sending the masses of data back to Wellington to render Serkis and his tribe into the range of expressive furry individuals who seem as real as the human cast.
They had some experience of doing mo-cap outdoors in the previous film, with scenes at the end of the movie filmed at San Francisco's famous Muir Woods.
"That had a sunny carpark right next to it so we had all the support we needed right there. It was baby steps. And figuring out how to you make the gear robust -- this was something going back to Kong. We've worked with Andy so much. Every show we do with him, all the gear we make, he just destroys it.
"We went to Weta Workshop next door and got them to rubberise some of the pieces for us and so it would withstand the Vancouver weather and what all the actors were going to do to it."
For Serkis, his second turn at Caesar might look more demanding than the first -- he's sure got a whole lot more lines -- but he says as the character has evolved, he's become easier to play.
Andy Serkis says while Dawn of the Planet of the Apes was a bigger part for Caesar, the character was easier to play.
"The physical toll was definitely much less. Caesar is bipedal for most of the time and he rides a horse. He's more human in his physicality so I'm not quadrupedalling as much as the other actors."
Serkis has been acclaimed for his abilities in performance capture roles. But though he's become a specialist in the field -- developing his own Imaginarium studio in London specialising in mo-cap anthropomorphism -- he doesn't think what he does is special.
"I just act. With performance capture, there is no mystery to it. If you go back to the original 1968 Apes for example, if I was Andy Serkis playing Roddy McDowall's part in the original, I would be wearing very thick makeup and a costume.
"I would be finding a way to be an ape and it would be exactly the same process as what I do now, or say, when Meryl Streep played Margaret Thatcher. When actors transform, they are doing what I am doing. I am just not putting on costume and makeup, but the process is no different."
Nor is he too fussed about the debate about whether he's more a special effect enabler than an actor.
"The question is about authorship of a role," he says. "Although the visual effects world and the work on this film is utterly extraordinary and a groundbreaking move forward, we have to look at why the audience feels what they do towards these characters. "And that is purely because of the actors and their performances.
"Playing a character using performance capture technology is only a technology; a bunch of cameras filming their performance. The audiences want to be moved, that doesn't happen by a visual effect; that happens by an actor's performance."
For Seresin, shooting a film in 3D while Weta Digital was shooting their own performance capture had its challenges. But though the mo-cap might add another layer, the same basic rules apply.
"The principles of storytelling with light, shadows, lenses, camera movement, remain constant -- unchanged since film started. The methods change, but the principles remain the same."
Letteri said it was up to Seresin, in tandem with director Reeves, to create the visual mood and style for the film that Weta would follow in their animation process.
"So he lit Andy and he lit all the ape actors as if they were appearing in the film as they were, which was great because then we could carry through with his ideas. He laid the groundwork and the style for us."
Though it sounds like Letteri would rather Reeves hadn't chosen the damp north to shoot in. That wet weather can sure play havoc with all those digital follicles.
"Fur is hard to begin with because you have hundreds of these strands on every body and you do have to simulate them. They have to move in the wind or when the body moves or when they are brushing up against something or are pressed -- and now you have little droplets that come in a pull on them and run down. Yeah, it is another whole layer of simulation you have to do on top of everything else."
They might have looked a bit wet and cold but no, no real animals were harmed in the making of Dawn.
But some animators were, says Letteri. "Oh yeah, they were put under some stress," Letteri chuckles as he signs off, heading back to a day toiling in front of a hot computer screen, helping ensure sure a small furry-footed fellow and his mates get to the cinema on time, for a third and final time.
What: Dawn of the Planet of the Apes
When and where: In cinemas from today
- TimeOut, Additional reporting Michele Manelis
