Princess of Wales: How might have Kate's photo been altered?
The Princess of Wales has apologised for confusion over edits to a newly released photo which was pulled by several major photo agencies over concerns the image was "manipulated".
The picture, taken by Prince William for Mother's Day, had been the first image released by Kensington Palace since Catherine's surgery in January amid intense speculation about her health.
But major photo agencies stopped distributing the image.
BBC Verify has spoken to experts about how the image might have been altered.
'Bad job of photoshopping'
BBC Verify has spoken to Prof Hany Farid, an expert in image analysis, who said the editing could be a "bad job of photoshopping".
He identified a missing portion of the cuff on Princess Charlotte's jumper and a blur on Catherine's right hand and in hair on the right of her face.
He said it was consistent with a couple of different explanations - poor photoshopping, artefacts of post-processing done by the camera to remove features like blurs, or a bad composite of images.
"There is a relatively new feature where you have a group of people, the camera identifies them through face detection, and it takes a series of photos in rapid succession," he explains.
"And invariably what happens when you take a photo of a group of people is somebody has their eyes closed or someone's not smiling, and so what this feature does is it looks at four, five, six, seven, ten photos, whatever, and composites them together.
"When it does that it sometimes makes mistakes."
Prof Farid could not find any evidence the image was generated by artificial intelligence (AI) after running it through his own dedicated system.
He also says there is nothing to suggest Catherine's face was added in after the photo was taken.
BBC photo editor Phil Coomes also identified the issue with Princess Charlotte's sleeve, as well as an issue near Louis's legs where there is what looks like a jagged edge on the base of a wooden door.
One possible explanation for some of the glitches would be if several photos were taken and shots were overlaid - perhaps because not all the children were smiling in a single image.
Questions remain around blurring on Catherine's right hand, and misalignment of her hair and the zip on her jumper.
There is also a green blur around Princess Charlotte's right knee which is inconsistent with the grey paving stones in the background.
Based on location makers like the white-framed windows and foliage, BBC Verify has identified the location of the photoshoot as Adelaide Cottage - the Windsor home of the Prince and Princess of Wales.
What editing is allowed by agencies?
Photo agencies have a very low tolerance for any digital alteration of images.
For example, the AP's photo standards allow minor photo editing, such as cropping and colour adjustments "when necessary for clear and accurate reproduction" - but say an image "should maintain the authentic nature of the photograph."
Backgrounds should not be digitally blurred, and changes to the contrast or saturation levels that substantially alter the original scene are not permissible.
Arthur Edwards, a Royal photographer for the Sun, spoke to the BBC and described the process of submitting photos to agencies.
"You photograph it, you can crop it, you can put a bit of sharpener on it if you have to... and then you send it," Mr Edwards said.
"You don't alter the actual picture itself. For instance, if one of the people in the picture has red eye, you can't take the red eye out, you have to leave it as it is."
What does metadata of the image show?
Kensington Palace said it would not be re-issuing the original unedited photograph of Catherine and her children.
But BBC Verify has analysed an image released by the agencies PA and Reuters. PA initially distributed the photo from the Palace to British news outlets under embargo.
Analysis of the image's metadata - data about the photo image - shows that the picture was taken with a digital camera using a Canon lens.
It was saved twice on photo editing software Adobe Photoshop, using an Apple Mac computer. But we do not know if both of these versions were saved on the same device.
The first version was saved on 8 March at 21:54 GMT, and the second was saved on 9 March at 09:39.
Metadata in the Reuters version of the picture does not include any information about Photoshop saves, and says the version was created at 11:34 on 10 March.
What did the Princess of Wales say?
Kensington Palace had initially declined to comment when news outlets like BBC News and photo agencies such as PA Media asked for further information about the images.
But in the last few hours, Catherine apologised and said she occasionally edited pictures.
She said in a written statement: "Like many amateur photographers, I do occasionally experiment with editing. I wanted to express my apologies for any confusion the family photograph we shared yesterday caused.
"I hope everyone celebrating had a very happy Mother's Day."
Have royal photos been edited in this way before?
Prince William and Catherine have previously issued their own photographs to the press and on social media.
The images are often taken by Catherine to mark special occasions, such as Father's Day. The princess is known to be a keen photographer.
While Catherine has acknowledged that she occasionally edits pictures, it is unclear if that includes previous official royal photos.
Royal biographer and photographer Ian Lloyd claimed the manipulation of royal photos was "nothing new" but that he had never seen the images criticised and withdrawn.
Additional reporting by Richard Irvine-Brown and Alex Murray
