Film, Sensor & ISO

Film & Types

Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts (bonded by gelatin) with variable crystal sizes that determine the sensitivity, contrast and resolution of the film.

Photographic Film

Most commonly films are classified into three major categories

Monochrome or Black and White film. Colour negative or print film Colour transparency or reversal film or slide film

Type of films

Black&White films are not available in wide range of film speed.

B&W film has very narrow exposure latitude.

Many black & white photographers believe colour distracts and emotion in the picture, whereas black and white highlights the form lighting and mood of the picture.

Black & White film

Colour negative films are available in wide range of film speed from ISO 25 to 3200

A negative image is a total inversion of a positive image, in which light areas appear dark and vice versa.

A negative colour image is additionally colour reversed, with red areas appearing cyan, greens appearing magenta and blues appearing yellow.

Colour negative films have a greater exposure latitude, hence it can be corrected up to three f-stops

Colour negative or print film

Saturation, rendering, sharpness, true colour and better reproduction quality are the advantages of reversal film over colour negative film

Before digital era, colour transparency were used in most professional magazines & slide projections

Colour Transparency Film has very narrow exposure latitude.

Colour Transparency or Reversal Film

Colour Transparency or Reversal Film

Film Developing and Printing Process

Load the film in the Developing reel Place the reel into the developing tank Then the Developing tank undergoes three chemical process

Chemical DeveloperStop BathFixerWashing & Drying the film reel

Film Developing Process

The Processed Film goes through Photo Enlarger where the Unexposed photo paper is exposed

The Exposed Photo paper undergoes the same chemical process as the film developing

Chemical DeveloperStop BathFixerWashing & Drying

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Printing Process

Image Sensor

Photo sensor is a device that converts an optical image into an electronic signal, which inturn converted into Digital Signal and stored for retrieval.

The Two Type of sensors used in Digital SLR are charge-coupled device (CCD) complementary metal–oxide–semiconductor (CMOS)

However Both types of sensor accomplish the same task of capturing light and converting it into electrical signals.

Sensors

CCD vs CMOS

crop factor is related to the ratio of the dimensions of a camera's imaging area compared to a reference format; most often, this term is applied to digital cameras, relative to 35 mm film format as a reference.

Crop Factor

Crop Factor

Film Speed ~ ISOInternational Organization for Standardization

Film speed is the measure of a photographic film's sensitivity to light, generally measured by International Organization for Standardization (ISO) system.

Based on the sensitivity of the film, it is determined as Fast or Slow Film i.e. if the film is sensitive then it takes less duration of time to record and hence its called Fast film and Vise-verse

Before ISO film speed is determined by DIN- Dutch Industries Norms, ASA - American Standards Association, BSI – British Standards Institution.

The ASA and DIN film speed standards have been combined into the ISO standards since 1974.

 Film Speed

 ISO control on light

Grain vs Noise

The Exposure Triangle

Limitations/Properties Triangle

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