Why is it you can replace some lights with more ‘advertised’ lumens with a LED light with less lumens. Here are 4 reasons why you can use less LED lumens to replace traditional HID lights
1. You need less lumens when you have Focused Directional Lumens
LED light is directional. Conventional light sources are omni-directional. They require reflectors to gather the light and focus it. Any reflection that is over 1 bounce effectively loses the effect of the lumen. It has been proven that you can lose up to 30% of the effective lumens in this process.
2. Quality of Lumens – you need less quantity when you have better quality
This is related to Color Rendering Index, or CRI. The best explanation is a simple test. Compare LED Light to High Pressure Sodium. It is not uncommon to have customers tell you that 20,000 lumens of LED appear brighter than 60,000 lumens of HPS. The basic truth is you need less quantity when you have higher quality. CRI is a scale between 0 and 100. It measures the quality of an artificial light source compared to a high quality light source, like the sun. Read more about CRI here.
3. Photopic and Scotopic Lumens
This has to do with how a camera perceives lumens and how humans perceive lumens. Photopic lumens are lumens detected by a light meter. Light meters register photopic lumens. Scotopic lumens are lumens detected by the human eye. LED produces light within our range of visible spectrum’s. The light created by LED is light we use. It is rare to see a LED light produce IP or UV spectrum. These wavelengths are invisible to people, so they have no value to us from a vision perspective.
Scotopic lumens uses a factor to adjust the photopic value of light. It gives a truer representation of how useful the lumens are. The factor, developed by scientists, is an attempt to level the playing field. The factor’s used to adjust the effective value of the lumen. This factor may move the photopic lumen up or down. HPS lights have a factor that reduces the effective scotopic lumen amount. LED has a factor > 1.7, which means the lumens it is producing is far more effective to us. Less photopic LED lumens are needed, where as more HPS lumens are needed to effectively light up an area.
4. Lumen Degradation
It is not uncommon for HID bulbs to have lost up to 50% of its initial lumens after only 5000 hours of life. Yet these bulbs are rated for 20000 hours. That means the customer is using a bulb that is performing poorly for 15000 hours of its life. As well, as lumens degrade, so does the quality of the light (CRI). And so the “effective lumens” of the light is dropping quickly.
We have been very successful replacing 400W Metal Halide bulbs with our 100W LED to HID Replacement Kit. The comments we here back is the light is brighter and the area is brighter. It currently produces 15,500 lumens.
Another example is 120W LED Bay Fixture producing 18,000 lumens. This is designed to replace upwards of 400W metal halide. If you have a bay fixture with a 400W Metal Halide bulb, this light is going to be a dramatic improvement over what you have.