I have a slideshow with photos in medium compression. If I open the slideshow
and add some new pages - will PPT perform a new compression om ALL PHOTOS or
just the added ones?

For instance when opening a JPG in Photoshop and re-saving it several times
causes a loss in image quality on every save. Is there a similair effect in
PPT that will cause all my includes images in the slide show to get lesser
and lesser image quality?

Thanks !