How many types of hologen and gas discharge are there?

This will depend upon the use of the system. Gas discharge lamps, particularly those with a very small plasma area are preferably suited for use with optical systems like lenses or reflectors. Therefore, the quantity of light aimed in the right direction can be far superior to a halogen lamp. Lumen output of such lamps is, generally greater than their incandescent counterparts. Conventional implies cannot be used to regulate the output of gas discharge lamps. It means that when regulation is needed mechanical irises or complex high frequency oscillators have to be utilized.

Halogen lamps are less costly, smaller and use simpler power supplies but provide less overall light. To light and side lighting applications, gas discharge is used generally, reserving the less powerful halogen light sources for decoration and effects. However, it must be said, that if the accurate halogen lamp, along with the right projection angle is used, good results can be acquired with small diameter harnesses.