PhotoJ notes

Two things that are essential for photojournalism that the camera obscura could not do would be that it can't zoom in or out on its images, and it doesn't have a flash or a shutter on it.

Emulsion is light sensitive gelatin and silver-halide crystals that help form images by condensing or dispersing on the images depending on if they are light or dark images. The dark images are the ones with not as many cluttered crystals as the light ones.