G for Grain: Grain and Noise Introduction

A silver halide (or silver salt) is one of the chemical compounds that can form between the element silver and one of the halogens. There are three common silver halide precipitates: AgI, AgBr & AgCl.

The grain is just the result of small chemical particles that have not received enough light.

The less light available when filming a scene the more grain you’re likely to see.

There are two types of Film grain in general Cubic and Tabular.

Cubic grain

The cubic grain is the traditional film grain which has a randomized structure of the grain as it has more of a “natural” feel to it.

Tabular Grain (T Grain )

Tabular-grain film is a type of photographic film that includes nearly all color films, T-grain films are more sensitive to variations in developer temperature, time, dilution, agitation, etc. Tabular grain technology brought significant improvements to the image quality of the film.

Noise :

The original meaning of “noise” was “unwanted signal” Digital Grain (Noise) also falls into two categories as well: Color and Luminance.

Color

Chroma noise shows up as discolored blotches, typically reddish and greenish. This is what contributes to that sickly look on skin tones and odd look of lighter colored solid tone objects such as walls.

Luminance

Luminance noise tends to resemble film grain – gritty or, at higher ISOs, a bit chunky.

Difference between noise and grain

The biggest difference is the patterns in the noise. Film grain is caused by the grains of silver present in the film, and are not in a consistent pattern.

ISO noise is caused in the digital sensor and is pixel based, and therefore in a pattern. film grain is more pleasing because of the inconsistent pattern.

Neither grain nor noise eats detail. It’s noise reduction that eats detail

Key Points in Grain :

Higher ISOs produce more noise
Digital films wouldn’t lose that “movie look” from the actual film. Now they add it to movies with a lot of CGI to blend the animation in.
If you reduce the film-grain you reduce the detail.
The size of the grains in the film varies depending on the film sensitivity.
The more sensitive the film, the larger the grains. Digital noise is always the size of a pixel, regardless of the ISO setting.
Digital noise consists of both luminance and color differences and is most visible in the blue color channel.
Although film grain is technically a defect (sometimes called film noise), it is highly sought after. Filmmakers have grown to love the look.
Film grain is sometimes more noticeable in the dark areas of a shot., the light areas are originally grainier because more light equals more clusters of silver halide. After processing, the underexposed parts of a shot are the grainiest.