technical: What film shall I use?
 

Grain

Another consideration is grain size. Do you mind if you can see the graininess of the particles that make up the image? Or do you want a print showing very fine detail, and no grain? Do you want a very big enlargement from a small negative without loss of quality?

The structure, size and amount of light sensitive silver halides in the film controls the speed and the graininess, so this has to be taken into consideration along with the light conditions. See diagrams below.

Move the pointer over each layer of film to reveal what it is for (requires javascript compatible browser - full text available in printer friendly version

diagram: cross-section of fast film, eg iso 400 Protective coating: this layer protects the delicate emulsion.  Although the surface can be cleaned with methylated spirits and a soft cloth, it is easy to scratch, crease or tear, so must be handled with great care. Any damage to this layer will make the negative unusable. Emulsion: this is the light sensitive layer; it contains silver chlorides, bromides and iodides suspended in gelatine. In a fast film there are more and larger particles than in slow film, and the emulsion is thicker. Silver halides react with light to create a latent image which cannot be seen until the development process has taken place. Film is so sensitive that exposure to light for a hunbdredth or even a thousandth of a second can cause an image to form. Film base: the film base is a translucent ribbon of cellulose acetate which holds all the other parts of the film together. It has to be strong enough not to tear in the camera and flexible enough to be wound tightly inside a film cassette. It has an anti-curl agent to help prevent negatives curling up inside the enlarger. Antihalation layer: this layer contains a dye which stops light reflecting from the base of the film back into the image, so preventing blurring of highlights. diagram: cross section of slow film. Protective coating: this layer protects the delicate emulsion.  Although the surface can be cleaned with methylated spirits and a soft cloth, it is easy to scratch, crease or tear, so must be handled with great care. Any damage to this layer will make the negative unusable. Emulsion: this is the light sensitive layer; it contains silver chlorides, bromides and iodides suspended in gelatine. In a slow film there are less and smaller particles than in fast film, and the emulsion is thinner. Silver halides react with light to create a latent image which cannot be seen until the development process has taken place. Film is so sensitive that exposure to light for a hunbdredth or even a thousandth of a second can cause an image to form. Film base: the film base is a translucent ribbon of cellulose acetate which holds all the other parts of the film together. It has to be strong enough not to tear in the camera and flexible enough to be wound tightly inside a film cassette. It has an anti-curl agent to help prevent negatives curling up inside the enlarger. Antihalation layer: this layer contains a dye which stops light reflecting from the base of the film back into the image, so preventing blurring of highlights.

As a general rule, fast film has more, larger, grains of silver halide than slow film. This makes the film more sensitive to light but also more grainy. Slow film has smaller grains of silver halide in a thinner emulsion which makes the image more fine grained and renders detail more accurately.

Protective coating: this layer protects the delicate emulsion.  Although the surface can be cleaned with methylated spirits and a soft cloth, it is easy to scratch, crease or tear, so must be handled with great care. Any damage to this layer will make the negative unusable. Emulsion: this is the light sensitive layer; it contains silver chlorides, bromides and iodides suspended in gelatine. In a slow film there are less and smaller particles than in fast film, and the emulsion is thinner. Silver halides react with light to create a latent image which cannot be seen until the development process has taken place. Film is so sensitive that exposure to light for a hunbdredth or even a thousandth of a second can cause an image to form. Film base: the film base is a translucent ribbon of cellulose acetate which holds all the other parts of the film together. It has to be strong enough not to tear in the camera and flexible enough to be wound tightly inside a film cassette. It has an anti-curl agent to help prevent negatives curling up inside the enlarger. Antihalation layer: this layer contains a dye which stops light reflecting from the base of the film back into the image, so preventing blurring of highlights.

Tip: If you want fine detail, or are making a big enlargement from a small negative, choose a slow, fine grained film. But be prepared to add extra light by using flash or studio lighting, or by placing the camera on a tripod so you can use slow shutter speeds to enable more light to reach the film.

Grainy image

photograph: a sports car shot on slow film

Fine grained image

photograph: a sports car shot on fast film