Plain radiography dates back to 19th century and the concept has remains the same since. However, with modern more sensitive detectors and computerised system, the images acquired can be further enhanced.

 

The best way to explain plain X-ray is by comparing it with the shadow on object casts when placed between a light source and a flat surface. The only difference is in X-ray, the source of the 'light' has penetrative energies, capable of passing through the human body. 

 

Limitation of plain X-ray is lack of information in spatial dimension and its reduced sensitivity for small lesions. Nonetheless it is widely used in trauma setting for fracture detection and also for health screening to examine the lungs. 
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