Sturken, M., & Cartwright, L., (2009). Visual Technologies, Image Reproduction, and the Copy. In “Practices of looking : an introduction to visual culture” (2nd ed., pp 183-222). New York and Oxford: Oxford University Press.

In this article we see an example of convergence at its best. Photography was first developed as something for medical, legal, scientific or portraiture uses. All of which were essentially private in nature but also very professional only orientated in who could practice the new artform.  Sturken makes the statement of “photography emerged as a popular medium not simply because it was invented, but because it fulfilled particular social demands of the early nineteenth century.” This is where we first see convergence with photography. It moved from the professional use only to the more recreational use, still as something only able to be practiced by a select few, but now as something that is able to be viewed by the masses in both private and public situations.
The next aspect of convergence in photography comes with the involvement of movement and the early ways of depicting movement through a series of photos viewed in rapid succession through a narrow opening, as in the Zoetrope.
This then developed further into the Stereoscope and the Kinescope, but each were for a single viewer from a single point of view.  Once the development of celluloid and the projector was perfected, the photograph was able to be transformed into the motion picture, at first with a slow frame rate, but as time has passed and technologies have improved, the frame rate has also increased and where the early films were rather jerky in nature, we now have films which are visually almost indistinguishable from what we would see with the naked eye.
These progressions have been bought about not only by technological advancements, but also due to consumer pressure and the interaction between the two.
This development of the celluloid film, however, is where photography and film/cinema go their separate ways.  Celluloid seems to continue on in both, one as the film for movies, and the other as film for the film based cameras. Of course we now also have digital cameras in both video and still version and so the film is less involved, but it still remains as a valuable part of the development of photography, as well as cinema. Without photography, in my opinion, there would not be cinema. Conversely however, if cinema had been developed first and photography developed from it, without the first, the latter would not exist.  They are in effect intertwined very deeply, and although the two can now be viewed as separate entities, they are still very much part of each other.