Film grain is more than just a look; it’s chemistry. What our eyes see as grain is actually a chemical phenomenon of silver halide crystals reacting to light exposure. These crystals are scattered randomly over the film, which allows the photograph to develop in a pattern similar to how the photoreceptors in our eyes perceive images in real-life. This is in contrast to digital images, which use pixels arranged in electronic grids to create an image. The grain of a film image can also be measured. Like pixels, the grain is the smallest necessary unit to create an image. Ultra-fine grain film will be the clearest, with the least amount of variance in the picture quality. A larger grain is more sensitive to light, so the image may blend and contort to be more “grainy” than other sizes.