I love these questions when is a 5 watt bulb a 5 watt bulb?
The motor industry, sorry that is unfair the governments ministry of Transport, are still living in the 1920s. The output of light from a bulb should be measured in candela, lux, or any other kind of true measurement. The wattage that we use for bulbs in cars and many household bulbs is the power consumption of a tungsten filament incandescent bulb. The bigger the filament the more power or watts it consumes also the more light it produces. The colour of the light ie: yellow blue pure white is dictated by the temperature the filament burns at and the gas the filament is enveloped in.
Equatorial daylight has a temperature of 5800 Kelvin.
The rear bulbs fitted to our cars are tungsten filament bulbs with a temperature around 3200 Kelvin. Lux I would need to measure.
I now know why nobody has tackled bulbs light output.
Tungsten bulbs are the standard by which wattage is judged
A fluorescent tube has about three times the light output of tungsten bulb for wattage power consumption, and depending on the powder and gas makeup inside the tube can be at a temperature between 2800 & 6000 Kelvin
By putting halogen gas in a bulb you will get around 18% more light at around 2000 Kelvin hotter so whiter than an ordinary bulb
Discharge lighting would be the next step up a ballast strikes an arc between two electrodes which is then maintained. The colour of the light is affected by the gas in the bulb. Sodium will give you street light yellow, Mercury Vapour gives you a blue light. Depending on construction they can give you anywhere from two to three and a half the amount of lux developed by a tungsten bulb. When fitted to cars they are usually called xenon headlights.
Once the arc is struck they consume much less power for the same or more light and in cars are around 6200 Kelvin.
Then we come on to the wonderful world of Light emitting Diodes.
They have come on leaps and bounds in the past 10 years. They will progress further in the next decade.
You get between 5 and 7 times the amount of light per watt consumed by that of a tungsten bulb. So a 0.73watt LED bulb will give you the same amount of light output as a 5 watt tail light bulb.
LEDs can also give a temperature range of 2000 to 8000 Kelvin
A car headlight can not exceed 55 watts dipped and 60 watts on main beam. There is no restriction on the temperature of the light or the Lux or candela the bulb puts out.
Now you know why you are blind when a modern LED light car comes at you the bulb may only consume 20 watts of power but can be putting out 3 times as much light at a much higher temperature than your 55 watt halogen bulbed car.
Some day the light output of a bulb will be measured in the proper way but how do we educate ourselves to understand what the numbers all mean.
Did you know that many of the LED bulbs sold today are computer printed.
I wish I had never started this post. But it is all good information.
Alan
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