The royal's first official portrait was unveiled earlier this month and Emsley previously admitted to being hurt by the "vicious" criticism of his work.
"I wanted to do something which had some sort of a sense of mystery, of presence, of stillness about it," Emsley told The Washington Post.
He added that he hoped to capture Kate's "natural, not official, self".
Emsley said: "I did not deliberately age her or anything like that.
"I wanted it to be an authentic record, but it's very easy to put in more shadows and things than are perfectly necessary, and I haven't done that.
"I've tried to record, in a polite way, what I regard as her natural beauty."
Of the Duchess's comments that the portrait was "amazing" and "brilliant", Emsley said: "I had the sense that she did get my work, that she understood what I was trying to do."
Regarding the criticism of the work, the artist said: "Those particularly vicious and personal comments at one stage made me feel, 'Gosh, was it wise to have gone through all this?'
"I have to accept the fact that there are many people that don't like the portrait, and that's fine. As an artist, you do understand you're never going to please everybody."
Duchess of Cambridge - a year in the life: photo gallery:
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