Keira Knightley posed topless for Interview magazine in September. And she's now revealing why.

The 29-year-old actress of "The Imitation Game" recently opened up about the semi-nude photo shoot in an interview with the British newspaper The Times, and confessed that she took the pictures in order to stand up against excessive photo editing.

"I've had my body manipulated so many different times for so many different reasons, whether it's paparazzi photographers or for film posters," Knightley told the newspaper.  

"That [shoot] was one of the ones where I said: 'OK, I'm fine doing the topless shot so long as you don't make them any bigger or retouch.' Because it does feel important to say it really doesn't matter what shape you are," she explained.

Knightley, who is known for her slender figure, has made headlines for being subjected to heavy photoshopping in the past.

When the actress starred in 2004's "King Arthur," posters of the film noticeably enlarged her bust-size. The team behind the film incurred a wave of backlash due to the misleading promotion.  

"I think women's bodies are a battleground and photography is partly to blame," Knightley told the Times. "It's much easier to take a picture of somebody without a shape; it simply is."

"Whereas actually you need tremendous skill to be able get a woman's shape and make it look like it does in life, which is always beautiful," she added. "But our society is so photographic now, it becomes more difficult to see all of those different varieties of shape."

The actress also spoke on gender inequality and how the roles of women and men are still far too defined by dated societal standards.  

"I've got a couple of mates who are guys who have taken the decision to look after their kids and the s*** they face because they've taken that decision is absolutely shocking," she said, adding, "The amount of prejudice, the amount of taking the baby to the baby group and women turning round and saying: 'Oh, is it your wife's day off?'"