The Leveson Inquiry into the media is hearing evidence from staff at the Daily Mail and Mail on Sunday and their publisher, Associated Newspapers.
Daily Mail picture editor Paul Silva has detailed to the inquiry the rules he follows on using paparazzi photos.
These include establishing that the subject had not been harassed, he said.
Mr Silva will be followed by Mail on Sunday editor Peter Wright and Liz Hartley, who is head of editorial legal services for Associated Newspapers.
Mr Silva told the inquiry the Daily Mail had received "about a handful" of complaints about photos in the last few years.
He said he considered it acceptable to use paparazzi photos of people which were taken in public places.
Someone's driveway would not be considered a public place, but the pavement would be. "We are only talking about a matter of yards," he said.
For the past three or four years he had asked a number of questions about the photos submitted by paparazzi "automatically on every story," he said. These included whether the subject of the image had been harassed and what sort of lens had been used to obtain the shot.
If a photographer had followed a celebrity all day, they would have to justify that, he said. "There would have to be a special reason for them being there that long, for that period of time."
Mr Silva said he asked the questions primarily to satisfy himself that the photos had been taken in the proper way before he put them forward for selection in the newspaper.
"Times have changed and we've had to change accordingly - and as a result of that we come up with these questions on every occasion when we deal with paparazzi pictures," he said. "We've reacted to the change in culture at the moment."
Mr Silva said that most shots of celebrities' children were not used but that if they were, the paper would check with the celebrities' agents or the children would be cropped out or their faces pixelated.
"We're very careful with regards to people's children," he said.
Mr Silva said the Daily Mail used photos of some celebrities more than others, depending on the interest they had for its readers. Since the royal wedding, Mr Silva said the Daily Mail had not used paparazzi photos of Pippa Middleton.
"At the moment we have a situation where there must be nine or 10 agencies outside her door," he said. "There's no reason to use them, there's no justification to use them."
He said the Daily Mail would use photos of Miss Middleton at events but "her just coming out of her door every day, there's no reason to use it."
Daily Mail picture editor Paul Silva Mr Silva said the Daily Mail had to be 'very careful with regards to people's children'
Hugh Grant's baby
Mr Silva said the Daily Mail had tried to get photos of actor Hugh Grant and his baby at the child's mother's house because it was a major showbusiness story.
"The purpose of going to the house was to see if we could get a close-up photo of Hugh, or mother with baby."
He told the inquiry that the Daily Mail had tried to obtain a photo consensually and that the story was considered a public matter because an agent had issued a statement confirming the baby's birth.
"There was no inclination [sic] in that statement that there was a privacy problem or a problem ahead."
Mr Silva said the newspaper's response to the birth had been consistent with how it had reacted when other high-profile people had had children.
"It's our normal response - it's the way we've done it for years," he said.
Mr Silva said no photo of the three together was obtained but that he believed it was acceptable for the Daily Mail to subsequently publish a photo of Mr Grant outside the his daughter's mother's home.
"He was there talking to photographers. I believe it was taken with his consent; he knew he was being photographed." Mr Silva said he did not ask the photographer whether consent had been obtained.
Counsel to the inquiry Robert Jay QC questioned Mr Silva about Kate and Gerry McCann, whose daughter Madeleine went missing in Portugal in 2007.
Mr Silva admitted that the Daily Mail had used unpixelated pictures of the McCanns' other children against the newspaper's general policy
"This was a unique situation … where we'd been allowed to stand in a certain position … and take pictures of the children."
But when asked whether he should not have used the pictures, Mr Silva said: "In hindsight, possibly … but there was no objection raised at the time."
Editors and executives
Later on Wednesday, the inquiry will be read statements by Associated Newspapers group managing director and chief executive of parent company A&N Media Kevin Beatty, as well as A&N Media finance director James Welsh.
The inquiry's focus this week has been on newspaper editors and executives.
On Tuesday, it heard evidence relating to the Financial Times, Independent and Telegraph broadsheets, while Monday's evidence concentrated on the Sun.
On Thursday, representatives from Northern and Shell - including Daily Express and Daily Star owner Richard Desmond and two of his editors - will give evidence.
Opening Wednesday's hearing, Lord Justice Leveson said some media had reported on comments he had made to witnesses as if they were preliminary findings. They were not, he said.
Prime Minister David Cameron established the Leveson Inquiry in July 2011 amid new revelations of phone hacking at the now-shut News of the World (NoW) tabloid.
A second phase of the inquiry will commence after the conclusion of a police investigation into NoW phone hacking and any prosecutions. It will examine the extent of unlawful conduct by the press and look at the police's initial hacking investigation.