(CNN) -- BP said Thursday it has removed a second substantially altered photo from its Gulf of Mexico oil disaster website and has instructed its contract photographers to not make any more cut-and-paste changes to its images.
The acknowledgement of the doctored photo -- of a helicopter that appears to be flying over the Gulf near the spill site -- came a day after BP admitted it had posted an altered photo of engineers examining screens at BP's oil spill control center in Houston, Texas.
In both instances, the same contract photographer used cut-and-paste techniques in Photoshop to change some features of the images, BP spokesman Scott Dean said.
After removing the pictures from the site, BP posted them and the originals on its Flickr page so the public can compare them.
"We told the photographer not to do that [cutting and pasting] again, and he understands," Dean said, adding that BP has given other photographers the same instruction.
The latest photo to be identified as a doctored image is taken from inside a helicopter that appears to be flying over water. Websites such as Gizmodo noted suspicious features in the photo, including a control tower in the upper left corner, which would be incongruous for a helicopter flying over the water.
It turned out that in the original image, the helicopter was not flying, but resting on the deck of an oil rig or a ship. The photographer had altered the image in Photoshop, removing the deck and making it appear as if the helicopter were over water, BP said.
The other altered photo -- exposed by sites including AMERICAblog -- shows engineers examining screens at BP's oil spill control center in Houston.
The engineers were indeed monitoring images taken by remote-operated vehicles at the spill site, Dean said, but the photographer pasted scenes into some blank screens. The alterations made it appear as if the engineers were looking at more than they actually were.
Dean said he didn't know why the photographer altered the helicopter image. But he said Thursday that in the case of the engineers' photo, the photographer never meant for the alterations to be published.
The photographer pasted scenes into some blank screens just to demonstrate Photoshop techniques to colleagues, according to Dean.
"He told me he was simply showing colleagues how easy it would be to fill in the screens, and he inadvertently left it in that condition," Dean said.
BP, which has pledged transparency and openness throughout the oil disaster, said on Wednesday that the screens were altered to "enhance the quality of the photo," and that the photographer had no intention to mislead anybody. But the company did not mention then that the photographer meant the alterations as a demonstration.
BP also removed from its site a third photo -- one that it said could be mistaken for a cut-and-paste alteration. The photo, showing people looking at a screen at a BP operation center in Houston, was manipulated by a Photoshop color saturation tool so that objects that actually were on the screen would be visible, Dean said. Without the manipulation, the screen appeared blank.
That third photo, and the original, also are on BP's Flickr page.
The company is comfortable with photo alterations such as cropping and color correction, but cutting and pasting is going too far, Dean said.
A statement on BP's Flickr page says the photographer has been told to "refrain from cutting and pasting in the future and to adhere to standard photojournalistic best practices."
Mugur Geana, assistant professor of strategic communication at the University of Kansas, said it is fine for a company -- in nonadvertising, public relations situations -- and the news media to crop photos and adjust them for color saturation, contrast and brightness. But even then, he would advise companies and media outlets to disclose the changes if they were sufficiently important.
CNN's policy permits adjustment of brightness, contrast and color balance, though it doesn't allow alteration that changes the meaning of the photo. While CNN allows photos to be cropped to meet dimension and aspect ratio requirements, the crop must not change the meaning of the photo.
As for adding or subtracting things from photos, such as erasing an oil rig's platform in the BP image, Geana said that is a problem.
"Ultimately, that's lying," Geana said. He added it also undercuts what should be a goal for companies -- portraying a trustworthy image.
"In the control room [photo], they're adding images on those screens. The purpose is to say, 'Here is intense activity that we're having.' ... You're trying to create an image of the company that is artificial," Geana said. "What's happening now with BP, they were discovered, so they have a bigger PR problem than they had before."
Geana said he hoped this episode will encourage companies and media outlets to pay more attention "in terms of making sure the pictures they released are not altered."