There are many differences but the four most important are: Small fiber size. The LDI is available in 100um, 400um, or larger fibers. Linearity. The LDI is an extremely useful light source for quantitative imagine, with linearity tracked internally from 1% to 100%. Specificity. The wavelengths of light from the LDI are not broad in spectrum line an LED. They are highly specific, which is critical for fluorescent illumination. Stability. The LDI is a very stable light source, which enables both accuracy any precision of light measurements.