One of the earliest recorded incidents was December 5th 1891 a photograph taken by Sybell Coret of the library at Combermere Abbey in Cheshire, which revealed the translucent shape of an elderly gentleman sitting in a chair. The figure was later identified as that of Lord Combermere himself: but at the time the photograph was taken, he was being buried a few miles away.
Also a photograph taken of the inside of a church in Eastry, Kent, in 1956 depicts a ghostly type figure of a vicar. The photograph was shown to a Women's Institute group some years later only to hear stories of a phantom vicar who used to be seen during the 1940s. This may well be an example of what is called a 'Place Centred' ghost. A overwhelming attachment to the church could have been the reason why a 'record' of his image had been imprinted upon the photograph. However this is only speculation. There has never been any substantial evidence to come to such a conclusion.
When taking a photograph or still, the light levels are stored onto a film which is housed in a box which is void of all light, until that brief moment when the shutter is opened to allow any form of light images to be stored onto the film. The images stored are of light reflecting off the scene the camera was pointing at. The photographers only see the shot they look at through the lens, so why do images appear on the processed film. The processing of still photography requires chemicals to produce the negative which in turn allows prints to be made, so is it using certain chemicals that can cause blemishes and images which were not present when the picture was taken?
I think not ! There is no proof that these strange images are stored on the film before chemicals are applied to them, however, if there were it would certainly shed new light on the subject.