Everyone needs a little help understanding lighting terminology for the best comparisons to be made. Here are some definitions and examples in easy to understand terms:

Lumens
Probably the most common word in the lighting industry – but what is it and why does it matter? The answer might surprise you that lumens matter a lot less than you think. In easy to understand terms, “lumens” refers to the total amount of light emitted by a light source in all directions.  If you are comparing home light bulbs or wide flood lights, lumens is a decent way to measure them because the light goes in all directions, or at least widely and usually evenly across a certain direction. But when we are referring to directionally focused light, such as a spot beam or combo beam on a pod light, that total lumen figure means a bit less until we look exactly where all that light is focused. This is where we get to Lux. But before we do that we need to talk about Raw and Effective Lumens.

Raw lumens is a theoretical maximum output figure derived by multiplying the LED diode manufacturer’s maximum recommended output times the number of LED’s a lighting manufacturer puts in a lamp. For example a “3-Watt LED Diode” might have a raw lumen rating of 300 lumens. With 3-Watt LED’s x 30 diodes in a off road light, one might claim 9,000 lumens. But that is a pretty deceptive number. Most LED’s are not (and should not be) operated at maximum output or it will suffer lifespan losses due mostly to overheating… you wouldn’t run your car’s motor at peak RPM’s all the time without expecting failure either. The safe range for most LED’s is usually around 80% of the maximum spec. So, right off the top there’s about a 20% loss of output vs the raw lumen figure. Then there are losses due to reflector type, lens material, imperfections, and other electrical losses, all of which might add up to 30% – 50% loss of output in measured lumens. Measured lumens = Effective Lumens.

Effective Lumens is the actual measured output of the finished lamp, as measured by a machine. It is a much rarer figure to see because it takes dedicated testing on expensive lab equipment. Jammy has the goniophotometer and integrating sphere to make these tests. So, when you see “Effective” that’s the light you’re actually getting, not just an overblown estimate based on false pretenses. Realistically what you see from the driver’s seat when a Jammy OffRoad light is in use isn’t lumens, it is the light cast on objects in the distance, that’s called Lux – a much more important figure.

Lux
Defined as the amount of light reaching a certain spot away from the light source. That spot might be the road hundreds of feet in front of you, that deer running up from the ditch in the distance, or the tree line half a mile away. Lux is how well that area in the distance is illuminated by your light source. You’ll often see a spec for “Distance at 1 Lux”. But what is 1 Lux? To imagine 1 Lux here are some examples: Enough light to read a newspaper; or the amount of light from a full moon on a clear night that casts hard shadows; or the amount of light from a standard candle 1 meter away. I think you get the idea.

You might also commonly see figures for Lux at 10 Meters, an up close reading; or Max Beam Distance, which is understood to be at 0.25 Lux. At this low 0.25 Lux number it is akin to the light cast by a dim moon – enough light to make out shapes but not enough to see details or read by.

Whatever the case, lux is is how much light is actually hitting a target in the distance. It’s what you are actually seeing as a driver. But the more interesting thing about lux is that it isn’t just one number like lumens… it varies depending on the shape of the beam and the distance from the light source. It varies so much that there could be thousands of test points that come together to produce the complete beam pattern.  The road, the trees, and the deer all have different amounts of light hitting them. That is why you’ll see common figures: Lux at 10 meters, Distance at 1 Lux, and Maximum Beam Distance (0.25 lux). But how do we derive lux? We do it with a peak candela measurement often coupled to a beam pattern report.

Peak Candela
This the brightest point of light intensity produced by a light source in its strongest direction. This is one that really matters. One can calculate lux based on peak candela. So, basically if we know how bright a light shines in one direction we can tell how much it will illuminate an area in the distance along that same vector. This is what is shown on a ISOLUX beam pattern chart. You can use it to understand a beam’s shape and distribution.

A light with high peak candela does not necessarily produce more total light (lumens); it means the light is focused more tightly, allowing it to project farther. Think about a flashlight. It might shine a very tight beam a long distance or it could be spread very widely across a shorter distance. It would have the same lumens either way, but peak candela would be greater for a focused beam and much less for a wide flood beam. Based on your needs, you might want both (wide and far) and that’s what a combo beam is meant to do. Spot is tight and far, flood is wide and short, combo beams blends both.

Rayleigh Effect
Did you ever put on your bright lights in the rain or fog just to realize that the light reflects back and blinds you? Have you noticed how yellowish lights tend not to have the same scattering/blinding effect? This is the Rayleigh effect. Basically different light colors are reflected differently by small particles, like sand, fog, snow, and rain. Bright white colors scatter more; yellow/amber colors scatter less. This is why some choose lights that produce Amber or Yellow light in the 2000 – 2500 Kelvin (K) light color range. This range is where the rayleigh effect is minimized while visible distance is maximized. The smaller the particles you want to cut through, the closer to 2000K you need to be. Fine dust and fog are very small particles. Rain and snow are a bit larger. Most white off road lights operate in the 6000k – 6500K range and even some as little as 5000k. But you’ll get a whited out using any of these white lights in the rain, crawling through fog or caravanning up a trail with dust in the air. Jammy OffRoad lights are available mostly in 2000K (Amber) with some options in 2500K (Yellow) – we even have a split hybrid double row light bar for the best of both worlds.

If there are figures you need help with or product recommendations based on what you’ve learned here, give us a call, or drop us a DM. We’re always happy to dig deep and explain what makes Jammy OfffRoad lighting work so well to Light Your Trail.