What happens to the characteristic curve as the development time increases?

When development time increases, the characteristic curve of a radiographic film becomes steeper and shifts to the left. This phenomenon occurs because an extended development time enhances the contrast of the image; areas with higher exposure become more pronounced, which leads to a sharper delineation between different levels of exposure.

A steeper curve indicates that a small change in exposure will result in a larger change in density, effectively improving the image's ability to differentiate between subtle variations in thickness or density of the material being tested. The leftward shift signifies that less exposure is required to reach the same density level, again a result of the film being more sensitive due to the prolonged development process.

In essence, a longer development time improves the film's sensitivity and contrast, which are crucial in radiographic testing for revealing flaws or inconsistencies in a material.