I had someone send me a PowerPoint file and my job is to convert it to web pages. I told him that I wanted the original sources for the images, which are jpgs, because it is my impression that the closer I get to the original source, the better I can make the images look on the web.
He did not want to bother with getting me the original sources (mostly from his own camera) because he did not believe there would be any difference. His main reasoning was that he claims the images in the PP file all have the same file size as the originals.
I know the jpg format is lossy and I would be very surprised to learn that pulling those images from PowerPoint is no different than having the original source.
Are the images linked or embedded? If they're linked and the author just used the originals, then you have the original source files (so I assume that's not the case or you wouldn't be asking).
Assuming they're embedded images, does he have "picture compression" turned off in PPT? If not, I'd assume he's compressing for the target size and there may be some quality loss.
I think most manipulations of size, sharpness, hue, etc will result in some loss of data, but if the images have not been manipulated much and you can get a resolution that is larger than what you'll need on the web pages, I would say to drop it and leave well enough alone. If he doesn't like the image quality, tell him you used what you gave him.