Kate regularly takes the official portraits of her children to mark special occasions.
The Queen passes on the responsibility after 67 years, having become a patron of the society in 1952.
Mum-of-three Kate Middleton arrived at a workshop to celebrate her new role as a patron of the Royal Photographic Society today.
Kate, who has a passion for photography, joined a workshop where professional photographers, who are honorary Fellows with the RPS, put youngsters supported by Action for Children through their paces.
Along with the message, the account shared a number of pictures, including some of The Duchess's photographs taken over the past few years of her family.
Shortly after the news broke, the duchess attended a photography workshop at Warren Park in Kingston, England.More news: Former Afghan PM praises Pakistan's Gulbuddin Hekmatyar role in peace process
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The public has mostly been treated to portraiture taken by the Duchess, who has shared several photographs she has taken of her children.
She said: "He was just misbehaving and hyper and struggled with social situations but now he's so much better, it's brought us closer together and made him likeable to be around".
"Just look at everything around you", the Duchess of Cambridge said. Maybe it's in front of you, or far away but choose your subject and focus in on it", Middleton advised, adding, "Get outside with your camera as well.
The Duchess of Cambridge is known to take her children's royal portraits, which are often shot outside of their country home in Norfolk. "George and Charlotte love it when we do that".
Before being on hand to capture snaps of her first day at nursery school.
She is joining children from Action for Children - which supports disadvantaged youngsters from across the United Kingdom - in several sessions, run with Royal Photographic Society honorary fellows Jillian Edelstein and Harry Borden.