Halogen – Quite obsolete: usually low voltage but intense illumination. Colour temperature is not ideal for colour photography.
LED – Modern microscopes are equipped with LED: low voltage but intense illumination. Colour temperature is ideal for colour photography.
HBO – High energy illumination specially dedicated to fluorescence microscopy. Fluorescent illumination offers a more desirable colour temperature (4100º Kelvin) with a "whiter" field of view and is more comfortable to the eyes.

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