LED has replaced halogen in most general lighting — but for retail accent, colour-critical display and dimming performance the older technology still holds its ground.
Halogen bulbs are essentially incandescent bulbs with a small quantity of halogen gas — usually iodine or bromine — inside the envelope. The gas allows evaporated tungsten to redeposit onto the filament, doubling the lamp's lifetime and permitting a hotter filament with correspondingly higher efficacy and CRI.
For accent lighting, gallery display, jewellery retail and any colour-critical application, halogen's CRI of 100 remains the reference against which all LEDs are still measured. No LED currently on the market reaches it.
Halogen also dims perfectly. Unlike LED, there is no flicker at low output, no minimum brightness threshold, and no compatibility matrix to consult against a wall dimmer.
The trade-offs are heat, energy consumption and the increasing regulatory pressure of European ERP and similar frameworks. For general-lighting replacement, LED filament has won. For specialist applications, halogen still has its place.