How an image is formed

Focus and flash are two things that are essential for photojournalism that a camera obscura could not do.
Emulsion is a light snesitive gelatin and silver-halide (a solid held in suspension)
Digital cameras, and film cameras both turn light into electricity. The differences between the two are: CCD sensors create high-quality, low-noise images. CMOS sensors are generally more susceptible to noise. CCD sensor are more muture because they have been mass produced for a long time.