Film Speed

Write short note on film speed.
Answer. Film speed refers to the amount of radiation required to produce a radiograph of standard density.

Film speed is indicated over the label side of intra-oral film packet and also on the outside of film box or container.

Film speed in radiography

Factors determining the film speed are:
- Size of silver halide crystals
- Thickness of emulsion
- Presence of special radiosensitive dyes.
Film speed should determine that how much radiation and the exposure time are necessary to produce an image on the film.

Factors affecting X-ray film speed

For example, a fast film needs less radiation exposure because film responds more quickly; response of fast film is quick because silver halide crystals in the emulsions are larger. Larger are the crystals, faster is the film speed.
For identifying the speed of film an Alphabetical classification system is used. X-ray films are given speed ratings which range from A speed i.e. slowest to F speed i.e. fastest. Only D and F speed films are used for intraoral radiography. E-speed films are discontinued by Kodak.
American Dental Association and American Academy of Oral and Maxillofacial Radiology currently recommend the use of F-speed film.

D-speed vs F-speed film

F-speed film need 60% of exposure time of D-speed film and has comparable image contrast and resolution.
Use of F-speed film leads to less radiation exposure for the patient.
F-speed film is faster as compared to D-speed due to the larger crystals and increased amount of silver bromide inside the emulsion.

Radiographic film classification

Recently used F-speed films not only reduce the radiation dose to the patient but also provide stable contrast characteristics under various processing conditions.
Ekta speed films (E – speed films) are the only E-speed films which are used in clinics, as they allow good radiographic visualization with minimum radiation exposure.

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