As I read it, the first part of your research simply involves studying the history of pre-digital imaging. So you start with daguerrotypes, then move on to emulsion plates and dry plates and (the really great advance) George Eastman's film rolls, together with advances in photographic papers. You also need to refer to the introduction of colour and of positive films (i.e.slide photography).
Then you can go on to give a brief history of digital imaging.
'Image output' was, in the earliest days of photography, solely by REFLECTED light. (i.e.. a print was viewed in daylight, or in artificial light, with the light reflected off it entering the viewer's eyes). The introduction of positive film (slides) meant that images could be viewed by TRANSMITTED light, with that light passing through (rather than being reflected off) the image, resulting in the ability to achieve much higher contrast ratios.
Digital photography uses solely transmitted light for viewing images, with that light being created within the monitor, screen or projector that is producing the image.
Many charity shops (and lots of secondhand bookshops) have books on the history of photography (published prior to the introduction of digital imaging) for sale at really cheap prices. (Abebooks.co.uk has 40 of them for under a quid!). Also, just about every large public library will have something useful as well. You simply need to top up the information in those books with something about digital advances.