About difference between film grain and digital noise.
Film speed is roughly related to granularity, the size of the grains of silver halide in the emulsion, since larger grains give film a greater sensitivity to light.
Photographic film contains tiny crystals of silver halide salts, which are the light sensitive component. When the film is developed, these crystals are turned into tiny filaments of metallic silver, and in a black & white negative the image is made up entirely of these microscopic threads. The threads curl up and clump together, and this is what is conventionally called 'grain'.
In a colour film, tiny blobs of dye are formed along with the silver during the development process. The silver is then chemically removed from the film, leaving only this dye image. It is these small specks of dye that are called grain in colour film, although, strictly speaking, they are not grains at all.
The faster the film, the larger the clumps of silver formed and blobs of dye generated, and the more they tend to group together in random patterns and become more visible to the naked eye.
The apparent granularity of an image is influenced by the film emulsion, developer, development scheme and density of the negative/slide film (grain is most evident in 'middle' gray areas and least noticeable in the low values). The nature of the scene also has a great influence on the apparent film grain.
Some people think that film grain is essentially the same artifact as digital noise, and have the opinion that they look very similar, and are there for the same reasons. That is simply not correct. Digital noise is extraneous information superimposed upon the image, while film grain is the basic atomic pattern of the image. It is responsible for acuity, contrast, resolution and detail. Whereas film grain can add atmosphere to a photograph, digital noise is generally considered to be an unattractive addition.
Film grain can be very beautiful and convey texture and mood. It can be a deliberate art effect. Film grain can look desirable under the right circumstances, under the right conditions, and when the photographer is attempting to convey a certain feel to a scene. Let's see some examples:
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Film grain here creates a beautiful texture in this portrait.
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This image was taken in low light conditions and is slightly underexposed, and shows too much grain, especially in the shadow areas.
Keep in mind that granularity varies with exposure - underexposed film looks grainier than overexposed.
Photographic film contains tiny crystals of silver halide salts, which are the light sensitive component. When the film is developed, these crystals are turned into tiny filaments of metallic silver, and in a black & white negative the image is made up entirely of these microscopic threads. The threads curl up and clump together, and this is what is conventionally called 'grain'.
In a colour film, tiny blobs of dye are formed along with the silver during the development process. The silver is then chemically removed from the film, leaving only this dye image. It is these small specks of dye that are called grain in colour film, although, strictly speaking, they are not grains at all.
The faster the film, the larger the clumps of silver formed and blobs of dye generated, and the more they tend to group together in random patterns and become more visible to the naked eye.
The apparent granularity of an image is influenced by the film emulsion, developer, development scheme and density of the negative/slide film (grain is most evident in 'middle' gray areas and least noticeable in the low values). The nature of the scene also has a great influence on the apparent film grain.
Some people think that film grain is essentially the same artifact as digital noise, and have the opinion that they look very similar, and are there for the same reasons. That is simply not correct. Digital noise is extraneous information superimposed upon the image, while film grain is the basic atomic pattern of the image. It is responsible for acuity, contrast, resolution and detail. Whereas film grain can add atmosphere to a photograph, digital noise is generally considered to be an unattractive addition.
Film grain can be very beautiful and convey texture and mood. It can be a deliberate art effect. Film grain can look desirable under the right circumstances, under the right conditions, and when the photographer is attempting to convey a certain feel to a scene. Let's see some examples:
|
Film grain here creates a beautiful texture in this portrait.
|
This image was taken in low light conditions and is slightly underexposed, and shows too much grain, especially in the shadow areas.
Keep in mind that granularity varies with exposure - underexposed film looks grainier than overexposed.