Yes, that's manic funnyman Robin Williams inside the pitiful blond husk of a man who creeps his way through the new psychological thriller One Hour Photo.

It's a tribute to both Williams and his director, Mark Romanek, that audiences are managing to forget the vibrant, instantly recognizable actor and focus instead on Sy, a sad, lonely photo-shop clerk. 

Romanek, who also wrote the script, admits casting Williams was an out-of-left-field choice. 

"Robin is a personality we know and trust and love and to put him in that circumstance was very subversive," he says of the actor who has also explored his dark side recently in Death to Smoochy and Insomnia

Williams' transformation began -- appropriately enough -- in a photo lab. 

"We took a neutral photo of Robin and then played around with it in Photoshop," Romanek told The Post

"We made him paler and played around with his hair and glasses and came up with the look." 

The trick, then, was to keep that look intact for the three-month shoot. 

"I told him to keep out of the sun," Romanek says. "He had to dye his hair once a week so the roots wouldn't show. 

"And I wouldn't let him exercise. He bikes religiously, but I said, 'You can't be physically fit.'" 

But it was the glasses and the blue SavMart vest that truly altered Williams. "As soon as he put that vest on he became very repressed and uptight," Romanek says. 

Of course, the transformation went well beyond skin deep. 

"I'm not going to take a ton of credit for his amazing performance," Romanek says. "The advantage of him being this stunning mimic is that once he locked on to the syntax and the body language and the rhythm, he took to it astonishingly easily." 

Repressing his naturally effervescent personality took its toll on Williams -- who could only crack wise when the cameras stopped rolling. 

"He'd joke around a lot between takes," Romanek says. "He would have to blow off all the natural energy, release that comedic streak he has."

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