> Quick answer: The measured difference in light attenuation across a 15-meter radius when using a wide beam angle versus a focused spot lens at 2000 lumens cannot be quantified directly from the provided sources. While principles of beam distribution and intensity are discussed, specific data for this comparison is lacking.
The measured difference in light attenuation between a wide beam angle and a focused spot lens at 2000 lumens across a 15-meter radius remains indeterminate based on the available research. However, understanding the underlying principles can shed light on how these two configurations affect perceived brightness and illumination.
Core Principles of Light Distribution
Luminous flux (measured in lumens) is conserved but its spatial distribution affects illuminance (lux), which is lumens per square meter [1]. A focused spot lens concentrates 2000 lumens into a smaller area, resulting in higher illuminance at the center, while a wide beam spreads the same luminous flux over a larger area, reducing illuminance per square meter [1][11].
Human Perception and Contrast
Human eyes are highly sensitive to intensity changes, particularly within surrounding areas. A narrow beam can appear „brighter” due to its concentration of light [1][1]. For instance, a 100-lumen tight beam may seem brighter than a 500-lumen wide beam when viewed directly because the light is more concentrated in the former.
Working Distance and Beam Intensity
The working distance of a flashlight is defined as the point where illuminance drops to 0.25 lux, calculated by the square root of (beam intensity in candelas divided by 0.25 lux) [6][14]. A focused spot lens would achieve higher candela ratings than a wide beam lens, extending its working distance beyond 15 meters.
Optical Systems and Beam Distribution
Optical systems such as lenses and reflectors are designed to control light output. Lenses can diverge small-angle rays and converge large-angle rays for even illumination [5][12]. Reflector designs optimize directional light output with prism alignment affecting beam spread [9][19].
Human Perception and Comfort
The human eye adapts rapidly to changes in background illumination, making hallway lighting as low as 20% of room lighting [2][3]. Excessive brightness from a narrow beam can cause discomfort, while a wide beam may reduce glare but at the cost of lower illuminance per point [13].
Efficacy and Power Consumption
Luminous efficacy—the ratio of lumens to watts—varies with spectrum and design. White LEDs have lower theoretical maximums than monochromatic green light (555 nm) which peaks at 683 lumens per watt [4][10].
Practical Applications in Solar Lamps
In solar lamps, perceived utility is not solely determined by peak illuminance but also by uniformity and comfort. A wide beam may outperform a focused one due to reduced glare and visual discomfort [1]. This is especially important for environments like offices where visual fatigue is a concern.
Missing Data and Future Research
The sources lack specific data such as exact beam angles, candela ratings at 2000 lumens, or how illuminance attenuates with distance. Environmental factors like ambient light and atmospheric scattering can also influence attenuation at 15 meters but are not addressed in the research.
Key Takeaways
- A focused spot lens produces higher illuminance at the center than a wide beam.
- Human perception is highly sensitive to intensity changes, making a concentrated beam appear brighter.
- Optimal lighting design balances peak brightness with uniformity and visual comfort.
References
- [1] candlepowerforumscomthreadseasy-to-understand-lumens-vs-lux__e7e2b9c0 — reddit
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bright!". They both put out exactly the same amount of water/lumens though. Lux is the lumens per square meter on the target….so, the more lumens you have, the easier to spread them out and still have enough lux to see targets. If your beam spot is 10 square meters in size, you'd need ten times more lumens to have it look as bright as if it were focused down to only 1 square meter in size. IE: For the same "brightness", you'd need 1,000 lumens to get your 10 square meters to look as bright as the 1 square meter would look with only 100 lumens. This is why a guy with a 100 lumen light with a tight beam might say "its impossible to read with it because there's too much glare", but a guy with a 500 lumen floody beam can read the same page with no glare. 😀 Last edited:
- [2] US20040105264A1_-_Multiple_Light-Source_Illuminating_System__19ffc4dc — patent
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of the visible spectrum, but also wavelengths in the infrared and ultraviolet areas of the spectrum, and in other areas of the electromagnetic spectrum. – the minimum design criterion for intensity and spectrum differs for each application and is related to the end user who is the ultimate measuring instrument and economic consideration of the light provider. – the regularity of the changes in effects is derived from the user's perception. It is generally accepted that the eye cannot discern changes in beam intensity that are smaller than a factor of two to ten and color temperature differences of 200 to 300K. Illumination intensity changes are discernable as a logarithmic function and depend on background illumination levels. For example illuminating practice allows for hallway lighting to be 20% of room lighting due to rapid eye adaptation. However the eye is very perceptive of intensity changes when comparing images such as in comparison of gray scales and thus lighting for an art lay-up room must be very even. – a further improvement is where the lamp and lighting fixture function are carried out in one device. – a lamp with a symmetrical distribution in placed in a reflector to redirect the light, a requirement involving added cost of the reflector and performance inefficiencies. – PAR and other integral reflector lamps exist, they again have a symmetrical distribution in one of the axes and are large due to the high temperature of operation and requirement to distance r
- [3] US20040105264A1_-_Multiple_Light-Source_Illuminating_System__19ffc4dc — patent
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spectrum, but also wavelengths in the infrared and ultraviolet areas of the spectrum, and in other areas of the electromagnetic spectrum. – In designing a multi-light source luminaire the minimum design criterion for intensity and spectrum differs for each application and is related to the end user who is the ultimate measuring instrument and economic consideration of the light provider. The regularity of the changes in effects is derived from the user's perception. It is generally accepted that the eye cannot discern changes in beam intensity that are smaller than a factor of two to ten and color temperature differences of 200 to 300K. Illumination intensity changes are discernable as a logarithmic function and depend on background illumination levels. For example illuminating practice allows for hallway lighting to be 20% of room lighting due to rapid eye adaptation. However the eye is very perceptive of intensity changes when comparing images such as in comparison of gray scales and thus lighting for an art lay-up room must be very even. – A further improvement is where the lamp and lighting fixture function are carried out in one device. In a typical present-day lighting fixture, a lamp with a symmetrical distribution in placed in a reflector to redirect the light, a requirement involving added cost of the reflector and performance inefficiencies. While PAR and other integral reflector lamps exist, they again have a symmetrical distribution in one of the axes and are larg
- [4] Diodes_-_Education_-_DigiKey_TechForum_-_An_Electronic_Component__e6dec931 — authority
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that humans find useful. Measurements are typically quoted based on a photopic (color perception at normal light levels) vision model, in which the theoretical maximum is 683 lumens per watt. That maximum applies at the peak of the human spectral sensitivity curve around 555nm (green) so theoretical maximums for light sources with broader spectral content (e.g. “white” light) will be lower. Luminous flux , measured in units of lumens , is a measure of perceived optical power. Because human vision is not uniformly sensitive to all wavelengths, the usual all-purpose unit for measuring power (the watt ) doesn’t serve well in situations where providing illumination is the goal; one watt of red light does not provide the same illumination benefit as one watt of green light, for example. The luminous flux concept works around this limitation by weighting the spectral content of a light source according to a standard luminosity function, which describes the variation of human vision sensitivity as a function of wavelength. The various flux attributes used to describe LEDs communicate the amount of optical power produced by a device. These figures are directly dependent on the forward current applied to the LED when the measurement was made and somewhat less directly (though strongly) on the temperature of the device. Accordingly, the listed flux values are applicable at the also-listed test current and temperature. The photo below illustrates the difference in illumination benefit d
- [5] EP2263036A1_-_Optical_system_for_batwing_distribution__c4e10a40 — patent
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are mapped into larger values of φ. In order to provide much higher luminous intensity at higher angles, the lens both reduces the intensity at low angles and increases the intensity at high angles. The concave central section 510 diverges the small-angle rays, and the convex outer sections 512 converge the larger-angle rays. The profile ends at a maximum source collection angle θmaχ- [0044] The detailed profile can be calculated by various means. For example, the profile can be expressed as a polynomial in polar coordinates centered on the light source, and the terms in the polynomial can be optimized using Monte Carlo ray-tracing simulations. Alternatively, one can specify the desired output angle φ for each source ray angle θsource in terms of an angle output function φ(θsource). For a point source, there are various known methods for easily calculating the desired profile from such ray angle specifications. The profile can be calculated by any of these means, the resulting optical system performance can be simulated by Monte Carlo ray-tracing using a realistic extended source (not the simplified point source) , and a new, compensated angle function φ(θSOUrce) can be generated to correct the non-uniformities observed in the simulation. For example, in calculating the exemplary profile 500 using Eq. 4, when the profile was first calculated using a point source, the resulting optical system output exhibited too much luminous intensity at φ = 0. This effect was compensated by
- [6] Flashlight_-_Wikipedia__66ffc5a7 — wikipedia
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emitted is reported in lumens. Luminous intensity is determined by measuring the brightest spot in the beam produced by the flashlight, in candelas. Since this is a measure of all the light emitted in a solid angle (the "cone" of light in a particular direction), the beam intensity is independent of distance. The working distance is defined as the distance at which the maximum light falling on a surface (illuminance) would fall to 0.25 lux. This is comparable to a full moon on a clear night. The distance is calculated from the square root of (the beam intensity in candelas divided by 0.25 lux); for example, a beam intensity of 1000 candelas produces a working range rating of the square root of (1000/0.25), or 63 meters. The result is reported in meters or feet. The working distance is from the point of view of the user of the flashlight. A light directly pointed at an observer may be visible against a dark background for many times this distance, especially if the observer has night-vision equipment. Run time is measured using the supplied or specified batteries and letting the light run until the intensity of the beam has dropped to 10% of the value 30 seconds after switching on. The standard does not evaluate the behavior of the flashlight output during run time. A regulated flashlight may run at only a slowly declining output and then abruptly cut off, but unregulated types may have steeply-declining light output after only a short time. Manufacturers of headlamps may use
- [9] CA2855729A1_-_Light_reflector_cone_-_Google_Patents__59910ead — patent
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shown by the test data in FIG 5A, the total luminaire efficiency was 91%. Typical higher end commercially available fixtures designed for the same CFL may have approximate average efficiencies in the range of 65% to 78%, with the highest published efficiency found by the Applicant being 84%. Embodiments of the disclosed technology represent a significant increase in the total luminaire efficiency. The spacing criterion indicates 0.92, which is relatively narrow when compared to typical fixtures with CFLs that may have much wider beam angles that may give spacing criterion of approximately 1.3 to approximately 2. FIG 5B shows the experimentally obtained Candela distribution data of an example embodiment. The maximum brightness is 1513 candelas, which represents an approximate 100% increase compared to the previously mentioned commercially available light fixture with the highest published efficiency. According to certain example implementation of the disclosed technology, the orientation of the prism row features may be chosen based on the requirements of the intended application. For example, if the prism rows are aligned similar to that shown in FIG 2F when flat, then the resultant prism row alignment when formed into the cone shape may be relatively vertical. This alignment may give a more narrow light distribution for the reflector. In an example implementation, if the prism rows are aligned similar to that shown in FIG 2F-2 when flat, then the resultant prism row alignmen
- [10] Our_Best_Lamps_Still_Cant_Equal_the_Luminosity_of_-_IEEE_Spectrum__c5a4e3cc — authority
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# Our Best Lamps Still Can’t Equal the Luminosity of the Sun Source: Blog/Web URL: https://spectrum.ieee.org/our-best-lamps-still-cant-equal-the-luminosity-of-the-sun Author: Vaclav Smil Date: 2019-03-27 Illustration: Greg Mably You can roughly track the advance of civilization by the state of its lighting—above all, its power, cost, and luminous efficacy. That last element refers to the ability of a light source to produce a meaningful response in the eye, and it is the total luminous flux (in lumens) divided by the rated power (in watts). The luminous efficacy of direct sunlight rises with the solar altitude, going from 70 to 105 lumens per watt, and for diffuse skylight it ranges from 110 to 130 lm/W, for an overall global mean rate of around 105 lm/W. Under photopic conditions (that is, under bright light, when the retina’s rods are saturated and only the color-sensitive cones discriminate among wavelengths) the luminous efficacy of visible light peaks at 683 lm/W at a wavelength of 555 nanometers. That’s in the green part of the spectrum—the color that seems, at any given level of power, to be the brightest. For millennia, our sources of artificial light lagged three orders of magnitude behind this theoretical peak. Candles had a luminous efficacy of just 0.2 to 0.3 lm/W, coal gas lights did five or six times as well, and the carbon filaments of Edison’s early bulbs hardly did better than that. By 1898 Carl Auer von Welsbach introduced the first metal filament, and his o
- [11] LEDs_and_Lumens_Forum__a3fbd712 — authority
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mcd is light intensity. And yes, that's a rather useless unit for comparison. From wikipedia: "1 lx = 1 lm/m 2 = 1 cd·sr/m 2". Light intensity of two different light sources can only be compared when they've got the exact same specs for radiation angle and measuring distance from the source. Example: two light sources have the same amount of luminous flux but one of them as a a radiation angle that's narrow, the other wide. When measured from the same distance, and in the centre of the beam, the narrow beam will result in a higher reading than the wide beam. But then, (i.e.) 45 degrees off centre, the narrow beam may be reading less than the wide beam… So yes, a narrow beam of less total light output may indeed seem brighter (in the lit area) than a wide beam light. Apples and pears… It's probably why EU regulators first made regulations for unidirectional light sources and left the directional light sources out. Now the directional light sources must also be specified by the manufacturers in lumen and they must specify only the light in a cone of 90 degrees (there are exceptions). All light that falls outside that cone must not be specified. All of a sudded we found that a 50 W halogen spot light had less light output than a bog standard 40 W bulb? What? Apples and pears…, you can't compare them… Long story short… it all boils down to choosing the right beam angle for the application and then choosing the right amount of light output for the job. Did a bit more dig
- [12] EP2263036A1_-_Optical_system_for_batwing_distribution__c4e10a40 — patent
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a, or of any other compensation parameters, will vary depending on the effects being compensated, the size of the region to be illuminated, and other factors. [0046] FIG.6 shows a cross-sectional view of a radiation distribution system 600. The system includes a lens 606 having an output surface that is a surface of rotation about a longitudinal axis passing through or at least near the light source 612. Reflector profiles 602, 604 are dependent on the desired transverse illuminance I(0,y) . Similar to the lens calculation, the desired luminous intensity in the transverse axial plane inside the region to be illuminated is calculated by: However, the method of calculating the profiles is different. The cross-section of the system 600 is shown in the transverse symmetry plane of the lens 606, along with the projected angles in this plane of some sample rays. The reflector 602 intercepts any source rays with projected angles ranging from θi to Q2, and the reflector 604 intercepts source rays with projected angles ranging from θ3 to θ4. Note that the source rays exiting with projected angles θ2 to θ3 are uncontrolled .by the reflectors. The design must compensate for the uncontrolled light. The lens output distribution Py is the sum of the uncontrolled fraction Punc (not incident on the reflectors) and a controlled fraction PCOnt (incident on the reflectors), given by: Because the lens surface is rotationally symmetric about the axis passing through the source, the ray angles fro
- [13] CA2763884C_-_Led_luminaire_thermal_management_-_Google_Patents__839dab2b — patent
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main beam of light concentration. This discomfort is measured in candela/meter squared, and is quantified by measuring the exitance of light from the luminaire with relation to the angle said light is exiting from the light fixture. . , This wide distribution means that a large portion of the light emitting from the secondary optic is directed at the same region at a high angle to the luminaire (a generally horizontal plane). Since an LED array comprises many LED's, every LED contributing rays of light into this relatively small high angled area, the overall effect is that the luminaire appears a number of exceedingly bright spots. The brightness can cause significant discomfort to one who views the luminaire in the main beam of light concentration. This discomfort is measured in candela/meter squared, and is quantified by measuring the exitance of light from the luminaire with relation to the angle said light is exiting from the light fixture. . , [013] To resolve this high angle brightness, a tertiary optic is added to diffuse the directional light emitted from the first optic configuration to disperse light over a much larger surface area hence reducing the perceived glare from the luminaire. In this instance, disperse can be defined as; "to cause to break up" or "to cause to be spread widely", and can comprise the mechanisms of diffusion or diffraction. Diffusion can be defined as; "to permit or cause to be spread freely" or "to break up and distribute incident light by r
- [14] US12356527B1_-_Multimode_lighting_system_-_Google_Patents__19b45a32 — patent
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capability, and peak beam intensity. – Beam Distance is measured in meters and defined as the distance from the light where illuminance is equal to a full moon on a clear night. – Light output is measured in lumens and is a measurement of energy. – Impact resistance is measured in meters and is tested by dropping the light onto a concrete surface with all accessories and batteries installed, from a specified height. – Run time measured in hours, measures the amount of time until the flashlight's output drops below 10%. Tests are conducted with the same batteries as come with the unit, or with the batteries suggested by the manufacturer to be used with the product. – Water resistance is represented by an ingress protection (IP) rating. – Peak beam intensity is measured in candelas and is a measurement of the intensity at the center of the flashlight beam. – the promulgation of the FL-1 standard however has not been a panacea for flashlight consumers. – the portable lighting industry is driven by marketing high lumen values on products. This has created incentives to game the FL-1 Standard in ways that do not accurately convey light output performance to consumers. – inconsistent mode labels e.g., turbo, high, medium, low, ultra-low – icons in the FL-1 standard allow consumers a means of product comparison, the user interfaces on the products are inconsistent making it difficult for users to get the full benefit of the product purchased. – FIG. 2 is a graph 200 of light curves
- [19] US8534881B2_-_Light_reflector_cone_-_Google_Patents__09692e34 — patent
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optical film's surface. (score lines will be discussed in other example embodiments). As shown by the test data in FIG. 5A , the total luminaire efficiency was 91%. Typical higher end commercially available fixtures designed for the same CFL may have approximate average efficiencies in the range of 65% to 78%, with the highest published efficiency found by the Applicant being 84%. Embodiments of the disclosed technology represent a significant increase in the total luminaire efficiency. The spacing criterion indicates 0.92, which is relatively narrow when compared to typical fixtures with CFLs that may have much wider beam angles that may give spacing criterion of approximately 1.3 to approximately 2. FIG. 5B shows the experimentally obtained Candela distribution data of an example embodiment. The maximum brightness is 1513 candelas, which represents an approximate 100% increase compared to the previously mentioned commercially available light fixture with the highest published efficiency. According to certain example implementation of the disclosed technology, the orientation of the prism row features may be chosen based on the requirements of the intended application. For example, if the prism rows are aligned similar to that shown in FIG. 2F when flat, then the resultant prism row alignment when formed into the cone shape may be relatively vertical. This alignment may give a more narrow light distribution for the reflector. In an example implementation, if the prism rows a
bright!". They both put out exactly the same amount of water/lumens though. Lux is the lumens per square meter on the target….so, the more lumens you have, the easier to spread them out and still have enough lux to see targets. If your beam spot is 10 square meters in size, you'd need ten times more lumens to have it look as bright as if it were focused down to only 1 square meter in size. IE: For the same "brightness", you'd need 1,000 lumens to get your 10 square meters to look as bright as the 1 square meter would look with only 100 lumens. This is why a guy with a 100 lumen light with a tight beam might say "its impossible to read with it because there's too much glare", but a guy with a 500 lumen floody beam can read the same page with no glare. 😀 Last edited:
of the visible spectrum, but also wavelengths in the infrared and ultraviolet areas of the spectrum, and in other areas of the electromagnetic spectrum. – the minimum design criterion for intensity and spectrum differs for each application and is related to the end user who is the ultimate measuring instrument and economic consideration of the light provider. – the regularity of the changes in effects is derived from the user's perception. It is generally accepted that the eye cannot discern changes in beam intensity that are smaller than a factor of two to ten and color temperature differences of 200 to 300K. Illumination intensity changes are discernable as a logarithmic function and depend on background illumination levels. For example illuminating practice allows for hallway lighting to be 20% of room lighting due to rapid eye adaptation. However the eye is very perceptive of intensity changes when comparing images such as in comparison of gray scales and thus lighting for an art lay-up room must be very even. – a further improvement is where the lamp and lighting fixture function are carried out in one device. – a lamp with a symmetrical distribution in placed in a reflector to redirect the light, a requirement involving added cost of the reflector and performance inefficiencies. – PAR and other integral reflector lamps exist, they again have a symmetrical distribution in one of the axes and are large due to the high temperature of operation and requirement to distance r
spectrum, but also wavelengths in the infrared and ultraviolet areas of the spectrum, and in other areas of the electromagnetic spectrum. – In designing a multi-light source luminaire the minimum design criterion for intensity and spectrum differs for each application and is related to the end user who is the ultimate measuring instrument and economic consideration of the light provider. The regularity of the changes in effects is derived from the user's perception. It is generally accepted that the eye cannot discern changes in beam intensity that are smaller than a factor of two to ten and color temperature differences of 200 to 300K. Illumination intensity changes are discernable as a logarithmic function and depend on background illumination levels. For example illuminating practice allows for hallway lighting to be 20% of room lighting due to rapid eye adaptation. However the eye is very perceptive of intensity changes when comparing images such as in comparison of gray scales and thus lighting for an art lay-up room must be very even. – A further improvement is where the lamp and lighting fixture function are carried out in one device. In a typical present-day lighting fixture, a lamp with a symmetrical distribution in placed in a reflector to redirect the light, a requirement involving added cost of the reflector and performance inefficiencies. While PAR and other integral reflector lamps exist, they again have a symmetrical distribution in one of the axes and are larg
that humans find useful. Measurements are typically quoted based on a photopic (color perception at normal light levels) vision model, in which the theoretical maximum is 683 lumens per watt. That maximum applies at the peak of the human spectral sensitivity curve around 555nm (green) so theoretical maximums for light sources with broader spectral content (e.g. “white” light) will be lower. Luminous flux , measured in units of lumens , is a measure of perceived optical power. Because human vision is not uniformly sensitive to all wavelengths, the usual all-purpose unit for measuring power (the watt ) doesn’t serve well in situations where providing illumination is the goal; one watt of red light does not provide the same illumination benefit as one watt of green light, for example. The luminous flux concept works around this limitation by weighting the spectral content of a light source according to a standard luminosity function, which describes the variation of human vision sensitivity as a function of wavelength. The various flux attributes used to describe LEDs communicate the amount of optical power produced by a device. These figures are directly dependent on the forward current applied to the LED when the measurement was made and somewhat less directly (though strongly) on the temperature of the device. Accordingly, the listed flux values are applicable at the also-listed test current and temperature. The photo below illustrates the difference in illumination benefit d
are mapped into larger values of φ. In order to provide much higher luminous intensity at higher angles, the lens both reduces the intensity at low angles and increases the intensity at high angles. The concave central section 510 diverges the small-angle rays, and the convex outer sections 512 converge the larger-angle rays. The profile ends at a maximum source collection angle θmaχ- [0044] The detailed profile can be calculated by various means. For example, the profile can be expressed as a polynomial in polar coordinates centered on the light source, and the terms in the polynomial can be optimized using Monte Carlo ray-tracing simulations. Alternatively, one can specify the desired output angle φ for each source ray angle θsource in terms of an angle output function φ(θsource). For a point source, there are various known methods for easily calculating the desired profile from such ray angle specifications. The profile can be calculated by any of these means, the resulting optical system performance can be simulated by Monte Carlo ray-tracing using a realistic extended source (not the simplified point source) , and a new, compensated angle function φ(θSOUrce) can be generated to correct the non-uniformities observed in the simulation. For example, in calculating the exemplary profile 500 using Eq. 4, when the profile was first calculated using a point source, the resulting optical system output exhibited too much luminous intensity at φ = 0. This effect was compensated by
emitted is reported in lumens. Luminous intensity is determined by measuring the brightest spot in the beam produced by the flashlight, in candelas. Since this is a measure of all the light emitted in a solid angle (the "cone" of light in a particular direction), the beam intensity is independent of distance. The working distance is defined as the distance at which the maximum light falling on a surface (illuminance) would fall to 0.25 lux. This is comparable to a full moon on a clear night. The distance is calculated from the square root of (the beam intensity in candelas divided by 0.25 lux); for example, a beam intensity of 1000 candelas produces a working range rating of the square root of (1000/0.25), or 63 meters. The result is reported in meters or feet. The working distance is from the point of view of the user of the flashlight. A light directly pointed at an observer may be visible against a dark background for many times this distance, especially if the observer has night-vision equipment. Run time is measured using the supplied or specified batteries and letting the light run until the intensity of the beam has dropped to 10% of the value 30 seconds after switching on. The standard does not evaluate the behavior of the flashlight output during run time. A regulated flashlight may run at only a slowly declining output and then abruptly cut off, but unregulated types may have steeply-declining light output after only a short time. Manufacturers of headlamps may use
shown by the test data in FIG 5A, the total luminaire efficiency was 91%. Typical higher end commercially available fixtures designed for the same CFL may have approximate average efficiencies in the range of 65% to 78%, with the highest published efficiency found by the Applicant being 84%. Embodiments of the disclosed technology represent a significant increase in the total luminaire efficiency. The spacing criterion indicates 0.92, which is relatively narrow when compared to typical fixtures with CFLs that may have much wider beam angles that may give spacing criterion of approximately 1.3 to approximately 2. FIG 5B shows the experimentally obtained Candela distribution data of an example embodiment. The maximum brightness is 1513 candelas, which represents an approximate 100% increase compared to the previously mentioned commercially available light fixture with the highest published efficiency. According to certain example implementation of the disclosed technology, the orientation of the prism row features may be chosen based on the requirements of the intended application. For example, if the prism rows are aligned similar to that shown in FIG 2F when flat, then the resultant prism row alignment when formed into the cone shape may be relatively vertical. This alignment may give a more narrow light distribution for the reflector. In an example implementation, if the prism rows are aligned similar to that shown in FIG 2F-2 when flat, then the resultant prism row alignmen
# Our Best Lamps Still Can’t Equal the Luminosity of the Sun Source: Blog/Web URL: https://spectrum.ieee.org/our-best-lamps-still-cant-equal-the-luminosity-of-the-sun Author: Vaclav Smil Date: 2019-03-27 Illustration: Greg Mably You can roughly track the advance of civilization by the state of its lighting—above all, its power, cost, and luminous efficacy. That last element refers to the ability of a light source to produce a meaningful response in the eye, and it is the total luminous flux (in lumens) divided by the rated power (in watts). The luminous efficacy of direct sunlight rises with the solar altitude, going from 70 to 105 lumens per watt, and for diffuse skylight it ranges from 110 to 130 lm/W, for an overall global mean rate of around 105 lm/W. Under photopic conditions (that is, under bright light, when the retina’s rods are saturated and only the color-sensitive cones discriminate among wavelengths) the luminous efficacy of visible light peaks at 683 lm/W at a wavelength of 555 nanometers. That’s in the green part of the spectrum—the color that seems, at any given level of power, to be the brightest. For millennia, our sources of artificial light lagged three orders of magnitude behind this theoretical peak. Candles had a luminous efficacy of just 0.2 to 0.3 lm/W, coal gas lights did five or six times as well, and the carbon filaments of Edison’s early bulbs hardly did better than that. By 1898 Carl Auer von Welsbach introduced the first metal filament, and his o
mcd is light intensity. And yes, that's a rather useless unit for comparison. From wikipedia: "1 lx = 1 lm/m 2 = 1 cd·sr/m 2". Light intensity of two different light sources can only be compared when they've got the exact same specs for radiation angle and measuring distance from the source. Example: two light sources have the same amount of luminous flux but one of them as a a radiation angle that's narrow, the other wide. When measured from the same distance, and in the centre of the beam, the narrow beam will result in a higher reading than the wide beam. But then, (i.e.) 45 degrees off centre, the narrow beam may be reading less than the wide beam… So yes, a narrow beam of less total light output may indeed seem brighter (in the lit area) than a wide beam light. Apples and pears… It's probably why EU regulators first made regulations for unidirectional light sources and left the directional light sources out. Now the directional light sources must also be specified by the manufacturers in lumen and they must specify only the light in a cone of 90 degrees (there are exceptions). All light that falls outside that cone must not be specified. All of a sudded we found that a 50 W halogen spot light had less light output than a bog standard 40 W bulb? What? Apples and pears…, you can't compare them… Long story short… it all boils down to choosing the right beam angle for the application and then choosing the right amount of light output for the job. Did a bit more dig
a, or of any other compensation parameters, will vary depending on the effects being compensated, the size of the region to be illuminated, and other factors. [0046] FIG.6 shows a cross-sectional view of a radiation distribution system 600. The system includes a lens 606 having an output surface that is a surface of rotation about a longitudinal axis passing through or at least near the light source 612. Reflector profiles 602, 604 are dependent on the desired transverse illuminance I(0,y) . Similar to the lens calculation, the desired luminous intensity in the transverse axial plane inside the region to be illuminated is calculated by: However, the method of calculating the profiles is different. The cross-section of the system 600 is shown in the transverse symmetry plane of the lens 606, along with the projected angles in this plane of some sample rays. The reflector 602 intercepts any source rays with projected angles ranging from θi to Q2, and the reflector 604 intercepts source rays with projected angles ranging from θ3 to θ4. Note that the source rays exiting with projected angles θ2 to θ3 are uncontrolled .by the reflectors. The design must compensate for the uncontrolled light. The lens output distribution Py is the sum of the uncontrolled fraction Punc (not incident on the reflectors) and a controlled fraction PCOnt (incident on the reflectors), given by: Because the lens surface is rotationally symmetric about the axis passing through the source, the ray angles fro
main beam of light concentration. This discomfort is measured in candela/meter squared, and is quantified by measuring the exitance of light from the luminaire with relation to the angle said light is exiting from the light fixture. . , This wide distribution means that a large portion of the light emitting from the secondary optic is directed at the same region at a high angle to the luminaire (a generally horizontal plane). Since an LED array comprises many LED's, every LED contributing rays of light into this relatively small high angled area, the overall effect is that the luminaire appears a number of exceedingly bright spots. The brightness can cause significant discomfort to one who views the luminaire in the main beam of light concentration. This discomfort is measured in candela/meter squared, and is quantified by measuring the exitance of light from the luminaire with relation to the angle said light is exiting from the light fixture. . , [013] To resolve this high angle brightness, a tertiary optic is added to diffuse the directional light emitted from the first optic configuration to disperse light over a much larger surface area hence reducing the perceived glare from the luminaire. In this instance, disperse can be defined as; "to cause to break up" or "to cause to be spread widely", and can comprise the mechanisms of diffusion or diffraction. Diffusion can be defined as; "to permit or cause to be spread freely" or "to break up and distribute incident light by r
capability, and peak beam intensity. – Beam Distance is measured in meters and defined as the distance from the light where illuminance is equal to a full moon on a clear night. – Light output is measured in lumens and is a measurement of energy. – Impact resistance is measured in meters and is tested by dropping the light onto a concrete surface with all accessories and batteries installed, from a specified height. – Run time measured in hours, measures the amount of time until the flashlight's output drops below 10%. Tests are conducted with the same batteries as come with the unit, or with the batteries suggested by the manufacturer to be used with the product. – Water resistance is represented by an ingress protection (IP) rating. – Peak beam intensity is measured in candelas and is a measurement of the intensity at the center of the flashlight beam. – the promulgation of the FL-1 standard however has not been a panacea for flashlight consumers. – the portable lighting industry is driven by marketing high lumen values on products. This has created incentives to game the FL-1 Standard in ways that do not accurately convey light output performance to consumers. – inconsistent mode labels e.g., turbo, high, medium, low, ultra-low – icons in the FL-1 standard allow consumers a means of product comparison, the user interfaces on the products are inconsistent making it difficult for users to get the full benefit of the product purchased. – FIG. 2 is a graph 200 of light curves
optical film's surface. (score lines will be discussed in other example embodiments). As shown by the test data in FIG. 5A , the total luminaire efficiency was 91%. Typical higher end commercially available fixtures designed for the same CFL may have approximate average efficiencies in the range of 65% to 78%, with the highest published efficiency found by the Applicant being 84%. Embodiments of the disclosed technology represent a significant increase in the total luminaire efficiency. The spacing criterion indicates 0.92, which is relatively narrow when compared to typical fixtures with CFLs that may have much wider beam angles that may give spacing criterion of approximately 1.3 to approximately 2. FIG. 5B shows the experimentally obtained Candela distribution data of an example embodiment. The maximum brightness is 1513 candelas, which represents an approximate 100% increase compared to the previously mentioned commercially available light fixture with the highest published efficiency. According to certain example implementation of the disclosed technology, the orientation of the prism row features may be chosen based on the requirements of the intended application. For example, if the prism rows are aligned similar to that shown in FIG. 2F when flat, then the resultant prism row alignment when formed into the cone shape may be relatively vertical. This alignment may give a more narrow light distribution for the reflector. In an example implementation, if the prism rows a