VATICAN CITY -- The Vatican admitted Wednesday that it altered a photo sent to the media of a letter from retired Pope Benedict XVI about Pope Francis. The manipulation changed the meaning of the image in a way that violated photojournalist industry standards.

The Vatican's communications office released the photo of the letter on Monday on the eve of Francis' five-year anniversary. The letter was cited by Monsignor Dario Vigano, chief of communications, to rebut critics of Francis who question his theological and philosophical heft and say he represents a rupture from Benedict's doctrine-minded papacy.

In the part of the letter that is legible in the photo, Benedict praised a new volume of books on the theology of Francis as evidence of the "foolish prejudice" of his critics. The book project, Benedict wrote, "helps to see the interior continuity between the two pontificates, with all the differences in style and temperament."

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The Vatican admitted to The Associated Press on Wednesday that it blurred the two final lines of the first page where Benedict begins to explain that he didn't actually read the books in question. He wrote that he cannot contribute a theological assessment of Francis as requested by Vigano because he has other projects to do.

A Vatican spokesman, speaking on condition of anonymity, didn't explain why the Holy See blurred the lines other than to say it never intended for the full letter to be released. In fact, the entire second page of the letter is covered in the photo by a stack of books, with just Benedict's tiny signature showing, to prove its authenticity.

In this photo of a letter released by Vatican Media, retired Pope Benedict XVI praises a volume of books about the theological training of Pope Francis. The Vatican admitted Thursday that it blurred the final two lines of the letter's first page, where Benedict begins to acknowledge that he didn't read the books and doesn't have time to write a theological assessment of Francis as requested. Vatican Media photo via AP

The missing content significantly altered the meaning of the quotes the Vatican chose to highlight, which were widely picked up by the media. Those quotes suggested that Benedict had read the volume, agreed with it and given it his full endorsement and assessment. The doctoring of the photo is significant because news media rely on Vatican photographers for images of the pope at events that are otherwise closed to independent media.

Vigano read parts of the letter during a press conference launching the volume, including the lines that were blurred out. A journalist who attended the presentation, Sandro Magister, transcribed Vigano's comments and posted them on his blog. But Vigano didn't read the whole letter. The Vatican didn't respond to a request to see the full text.

Most independent news media, including The Associated Press, follow strict standards that forbid digital manipulation of photos.

"No element should be digitally added to or subtracted from any photograph," read the AP norms, which are considered to be the industry standard among news agencies.

Vigano heads the Vatican's new Secretariat for Communications, which has brought all Vatican media under one umbrella in a bid to reduce costs and improve efficiency, part of Francis' reform efforts. The office's recent message for the church's World Day of Social Communications denounced "fake news" as evil and urged media to seek the truth.