In photography, a distinction is made between negative and positive films. Slide films are positive films and are therefore also called slide positive films. The main difference to a negative film is that the images on slide films are correctly represented in their colors after development and do not have to be recopied.
Slide films are 35mm films with perforations on both sides for film advance. The image area available for shooting is 36 x 24 mm. The images are cut from the slide film and framed in a slide frame. Since the image size is unsuitable for direct viewing, there are small viewing devices and slide projectors with which the slides are projected onto a projection screen.
Slide films consist of several emulsion layers that react differently to exposure. They have a very decisive advantage over negative films, photo prints and color displays: slides have the highest contrast range and thus a high quality standard. The dynamic range of slides is 1:1,000 to 1:2,000 in terms of the ratio between the brightest and darkest image details. In comparison, photos have a dynamic range of 1:100 to 1:200; newspapers are even further below this.