What are relative exposure factors?
In this article:
- Relative Exposure Factors Adjust Exposure Charts for Different Films: These factors allow radiographers to convert exposure times from one type of industrial X-ray film to another while using the same radiation energy
- They Are Not Universally Constant Across Energies: Because different radiation sources emit varying energy spectra, relative exposure factors must be applied cautiously and are most reliable when radiation quality is consistent
- Commonly Referenced for Agfa STRUCTURIX Films: Exposure charts are often based on a standard film like D7, and relative exposure factors are used to scale exposure times for other films such as D4, D5, or F8
- Useful for Optimizing Inspection Efficiency and Image Quality: By applying the correct factor, radiographers can maintain consistent film density and contrast across different film types without recalculating entire exposure setups
- Best Applied with Stable Radiation Sources: These factors are especially effective when using gamma sources like Ir-192 or Co-60, which emit consistent radiation energy, making exposure adjustments more predictable
What are relative exposure factors?
“Relative exposure factors” can be used to convert an exposure chart for one type of film to another film, although still for the same radiation energy. These factors are not constant for different radiation energies and should, therefore, be used with some caution. Some examples of relative exposure factors for Agfa Structurix films are shown in table 1-9.
These are the factors by which to increase or decrease the exposure-time when using the types of film other than those for which the exposure charts have been prepared.
In view of the widely-varying quality of the radiation emitted by different types of X-ray equipment and the appreciably different characteristics of the various types of X-ray films made for industrial use, caution should be exercised in applying these relative exposure factors generally.
Darkroom technique too, plays an important role and a uniform manual or automatic development process is, therefore, essential.
With radioactive sources, which give a constant quality (hardness/energy) of radiation, the relative exposure factors listed can be used quite safely.