Grain vs noise
Grain is intentional, film-like texture; noise is unwanted digital speckling, often colored and strongest in dark areas.
See it
What it is
Grain is the visible texture of film, formed by the random structure of its light-sensitive material. Noise is unwanted variation from a digital sensor and its electronics. Both can look like speckles, but film grain usually reads as monochrome, irregular texture while digital noise can bring blotchy color and fixed patterns. Kodak Tri-X 400 is a familiar reference for pronounced black-and-white grain.
Reach for grain when a clean digital image needs tactility, age, or a less clinical surface. Treat noise as a capture problem: expose well, keep ISO only as high as needed, and apply noise reduction before adding any deliberate grain.
Gotcha: grain is not automatically tasteful and noise is not always ugly. Heavy grain can bury skin and small type, while fine luminance noise may look natural. Chroma noise, the red, green, and blue flecks in shadows, is usually the first thing to remove.
Ask AI for it
Give this clean digital photo a restrained Kodak Tri-X 400 character in Adobe Lightroom Classic: use the Effects panel Grain controls at Amount 25, Size 22, and Roughness 50. Keep the texture mostly monochrome and irregular, preserve eyes and fine edges, and remove red, green, or blue shadow speckles before adding the grain.