"For example, AGFA is 1.5-2.5. If your EI is below 1.5, the cassette was underexposed and the computer does not have enough information to display a diagnostically valuable image. Therefore, you would need to increase your technique, which would increase the EI.
"

Depending on how that particular Ei is calculated, an EI below 1.5 could merely indicate that the cassette recieved less than expected as collimation was completely within skin edge - not becuase poor exposure factors were used. On our old system it was easy to demonstrate this by imaging something at very low exposure settings but exposing most of the cassette. This would result in the object being very white (far too noisy to detect any real contrast) but the EI indicating it was very over exposed (as there was lots of the cassette outside of the object that had been exposed and thus was very black.

Our new AGFA system uses a different EI scheme and seems far more accurate, but I have yet to really test it properly. It is important to note that EI systems generally also need to be calibrated.

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