Cinematographer-turned-director Karthik Gattamneni says shooting his forthcoming Telugu directorial debut "Surya Vs Surya", mostly at night, was extremely challenging.

"Out of the 45 days we spent on shooting the film, nearly 40 days were spent on night shoots. It was extremely challenging not just for me but for my actors as well. Most of them found this experience nerve-wrecking as it required them to shoot at odd hours in the night," Karthik told IANS.

The reason the film was mostly shot at night because it's the story about a character, played by Nikhil Siddhartha, suffering from Porphyria, a rare disorder that stops production of haemoglobin.

"The character can't face any natural source of light, including the sun. A lot of people mistook this film as a thriller, going by the trailer. The title here refers to the conflict between a character named Surya and the sun," he said.

"It's also about the conflicts within the character Surya. Some of us have inner conflicts that we can't resolve or express. Along the course of the film, how does Surya overcome his inhibitions of life forms the crux," he added.

He describes the film as a journey of self-exploration of a character suffering from the rare disease.

Karthik's inspiration for the story came from a visit to a night school in Hyderabad.

"On the facade of this college building, it was written -- day time earners, night time learners. I walked into the classroom and found people of all sections, age group and walks of the society. I thought what would happen if someone from an affluent family comes here to study," he said.

"As I kept thinking, I decided to create a character who'd fit in this college. In order to place the character in such an environment, I designed him with the medical condition of Porphyria, said Karthik, who couldn't find a producer for three years for the project.

Finally, luck favored him at the right time.

"When I was working on 'Karthikeya' as a cinematographer, Nikhil casually asked me about my plans. I told him I'm interested in directing and when I narrated the story I had in mind, he said let's do it," he said.

"Nikhil believes that all the risky projects he has attempted so far have worked. He didn't mind about delivering a hit or flop. He wanted me to give him a quality film," Karthik confessed.

Thanks to Nikhil's back-to-back hits, finding a producer wasn't challenging.

"Once Nikhil came on board, people were ready to bet on him after the success of 'Swamy Ra Ra' and 'Karthikeya'," he said.

Calling Nikhil a great "team player", Karthik said working with him was a delight.

"Post the release of 'Karthikeya', I could feel the pressure of directing Nikhil. After delivering two hits in a row, there are high expectations on this film. But Nikhil always kept motivating me and it helped me to concentrate on completing the film.

"Surya Vs Surya", releasing on Thursday, also features debutant Tridha Chaudhary, Madhoo, Tanikella Bharani and Rao Ramesh in important roles.

Karthik chose Tridha because he wanted a heroine who wouldn't mind working at nights.

Besides the directing the project, he has also canned the shots.

"It's challenging, but at the same time easier from one perspective. I know what shots I wanted to capture and how to shoot it. Initially, I was little confused handling both because at times I'm bothered about the expression of my actors, while also worrying about the light on their faces," he said.