When all other factors are equal, there is a direct relationship between lumens and brightness. However, lumens are not the only factor that influences brightness. To put it simply, talking about brightness without mentioning light divergence patterns/light area is a form of hooliganism.
Lumen (Lm) is a unit of luminous flux. The light source in unit time, radiation to surrounding space, and cause vision energy, is known as luminous flux.
The light flux is measured in the physical system using an integrating sphere, and the light emitted by the light source is measured using a solid Angle element.
1 lumen = the luminous flux emitted per unit solid angle by a point source of 1 candela intensity
What we usually perceive as "brightness" is actually called "illuminance", which is the flux of light received by the surface of the object in the unit area, in Lux.
1 lux = illuminance produced by a point light source of 1 candela on a sphere with a radius of 1 m
1 lux =1 lumen luminous flux evenly distributed over an area of 1 square meter illuminance
The relationship between illuminance and lumens is:
Lux = luminous flux/illuminated area.
As a result, we now have a very intuitive understanding that luminous flux is a three-dimensional concept and illuminance is a planar concept. The illumination value varies with the irradiation area under the same lumen, that is, under the same light flow. The lower the illuminance, the larger the radiation divergence area. And vice versa, the higher the illumination in the focused area, the lower the illumination in the unfocused area.
Here's another example:
The luminous flux (lumens) is equivalent to the flow of water, which is how much water flows out, through, or into a second, and the flow of water is how much water flows out, through, or into a second.
The number of lumens of light flowing into a one-square-meter area is referred to as illuminance.
Water flow is critical. We not only need to see the flow of water but also to see the flow of water per unit area. That is, the river has a cross-sectional area of 10 square meters and a flow rate of 10 cubic meters per second; the river has a cross-sectional area of 1 square meter and a flow rate of 3 cubic meters per second, and the stream is swift. That is what illuminance means - whether something is bright or not is determined by illuminance, which is the amount of light received by the source.
Okay, now let’s back to our lighting system.
Based on the above theoretical foundation, we can conclude that the illumination of a specific position is not the same for a camping lamp and a headlamp of the same lumen due to the different ways of light divergence.
The light from the camping lamp is distributed evenly on all sides, making it ideal for close lighting and camping activities. The headlamp, on the other hand, emits a focused beam of light with high illumination in the focused area and little illumination in the non-focused area.
So, the more focused the headlamp, the better it is?
No, not at all.
Laser pointers are focused, powerful, and penetrating, but that's all. A powerful flashlight's beam also travels far, but at the expense of most of the illumination area.
Thus, everything shall be in moderation.
The powerful headlamp HS6R from FreasyGears features both flood and focused beams, which can work separately for different tasks, or simultaneously for multipurpose use with 1400 lumen and 170m throw.
In terms of the headlamp's focusing angle, we consider the normal angle range of the human eye. The light pillar should allow the user to see the desired area without having to rotate the angle frequently. In fact, human vision is sensitive at 10 degrees, 10 - 20 degrees can correctly identify information, and 20 - 30 degrees is more sensitive to dynamic objects. We can determine the appropriate focus range for the headlight column based on this viewpoint.
How do you determine the light column's focusing angle? It is determined by the properties of the LED lens as well as the optical structure of the lamp's reflection and transmission. All of these factors work together to control how the light is focused, as well as the angle and direction of the light, which is unfortunately left to the engineers.
Someone said, my headlamp lumen is very high ah, but why can not I see well in the fog?
It all comes down to light penetration. Different types of light penetrate differently. Red light, for example, has the greatest penetration, so traffic lights use red light to indicate prohibition. That’s why the HS6R - a combination of a far-reaching spotlight, a neutral white floodlight, and red light with separate switch controls, is so popular in outdoor activities.