More than three quarters of images sent to picture desks by PROs are of such poor resolution that they are not even considered for publication.
Twenty-nine picture editors from regional, national and international publications were interviewed last month by image storage and distribution company Pixmedia.
Most said they did not consider photographs that arrive without captions.
They said more than half of photos submitted did not carry labelling.
Interviewees included the picture editors from The Daily Telegraph, Associated Press and Newsquest Media Group.