Geometrical Qualities

The difference between the shape of the real object and the shape of its projected image

the difference between the size of the real object and the size of its projected image

Calculations

Magnification = SID/SOD

Image Size/Object Size = SID/SOD

Sharpness of the structural edges recorded int he image

Higher spatial resolution

higher resolution means two objects can be demonstrated to be smaller or closer together

Poor spatial resolution

caused by unacceptable levels of penumbra as compared to the umbra

Penumbra

blurry, fading partial shadow projected at each edge

Umbra

uniform darkness of the inner-most shadow

Radiographer's Job

eliminate motion

reduce OID

Reduce focal spot size

Increase SID

*Digital equipment parameters

Calculations

Penumbra = (FS x OID) / SOD

Sharpness = SOD/OID