How do I draw an exposure chart?
How do I draw an exposure chart?
The exposure chart should be drawn on uni-directional logarithmic paper. The material thickness (in mm) is plotted on the horizontal linear axis and the exposure value (in mA.min) on the vertical logarithmic axis. For a given kilovoltage (for example 150 kV), we can, using the previously described intermediate kV-thickness chart, determine that for an exposure dose of 8 mA.min a density of 2 can be obtained at a thickness of 4.5 mm and for an exposure dose of 200 mA.min, at a thickness of 15.2 mm.
These thicknesses, and the corresponding exposures, are then plotted on the graph paper to give points A and B, see figure 4-9. Drawing a straight line linking points A and B, the 150 kV line is obtained. In a similar way the lines for other kV-values can be drawn in the diagram, eventually resulting in the complete exposure chart of figure 4-9.
