A slide show could be a series of images or pages of knowledge, usually displayed on an outsized screen employing a video projector. The primary slide shows were finished photos on items of glass, to be later replaced photographic material slides within the Forties. Because the technology improved, overhead projectors began to be accustomed project an image on a screen and also the slides were created with clear slide media, regarding the scale of a chunk of paper. Printers might print text and pictures on this media or dry-erase markers may well be accustomed write and draw on the media.