How bright is 500 Ansi Lumen

Luminous flux explained - how bright is 1000 lumens?

Since the classic incandescent lamp was withdrawn from the market, consumers have lacked a clear variable with which they can assess the brightness of a light source at first glance. In the past, you could rely on lamps with the same wattage to shine with about the same brightness. But these times are over thanks to the LED. The wattage of an LED retrofit or LED luminaire does not provide any information about the amount of light. For this reason, the luminous flux has now established itself as a benchmark for determining the amount of light from a light source. But what is behind this physical measured value? Is it possible to determine whether a light source provides the desired brightness based on the luminous flux alone? Or to put it another way: How bright are 1000 lumens?



Luminous flux in lumens - The brightness of lights and lamps

How much light does a conventional light bulb emit?

In order to answer these questions, we first have to understand what is hidden behind the term lumen: Lumen is the unit in which the luminous flux is specified. This describes the amount of radiation in the range of visible light that a light source emits. Put simply, the lumen value indicates how much light a lamp emits. First of all, it seems to be a reliable benchmark for comparing different light sources. Especially since the wattage no longer provides a reliable indicator of the brightness of a lamp due to the so-called incandescent lamp ban. But how can we compare different light sources with one another? Or to put it another way, how bright does a light source have to be to replace a 75 W incandescent lamp, for example?



Luminous flux in comparison

In the days of the incandescent lamp, the brightness of different lamps could be compared with one another using the wattage. With LED lights, LED retrofits or energy-saving lamps, the wattage does not provide a clear indication of the brightness of the light source. Only the unit of luminous flux in lumens helps here. A 75 watt incandescent lamp - one of the most widely used light sources before the ban on incandescent lamps began - generates a quantity of light of almost 1000 lumens. In order to replace a corresponding light source, an LED or energy-saving lamp with approx. 1000 lumens is required. But is the calculation that simple, or do other factors have to be taken into account when comparing lamps?


It's actually not that simple. Incandescent lamps emit their light evenly in all directions and have a beam angle of more than 270 °. These essential factors for light perception are not taken into account when specifying the luminous flux. This is particularly tricky because most LED luminaires and retrofits focus the light more strongly due to their construction. For this reason, many LED lights and lamps illuminate a smaller solid angle than the classic incandescent lamp. In the field of LED retrofits, there are now products that come very close to the incandescent lamp. LED filament lamps in particular are similar to classic incandescent lamps in terms of their radiation characteristics.


That's how bright 1000 lumens are compared to ...
... 700 lumens ...
... and 400 lumens

Let's take an example to illustrate this: The Euclid PD S dim2warm from the German lighting manufacturer Bruck emits a luminous flux of a total of 1000 lumens. The LED pendant luminaire thus basically qualifies as a replacement for our example with the 75 watt incandescent lamp. However, it focuses its light downwards. As a result, the area below the pendant light is brightly lit, while the surrounding area and the rest of the room remain relatively dark. Euclid thus provides accentuating zone lighting that is ideal for illuminating a table surface. However, it is not suitable as room light for general and general lighting.


1000 lumens are not the same as 1000 lumens. In order to be able to compare the brightness of light sources, the spatial aspect must also be taken into account: How far is the light source from the illuminated object, at what angle is the light emitted and how much light hits the illuminated surface? With that, however, we are already entering the subject of illuminance and luminous intensity, which are given in lux or candela. These variables relate the luminous flux to the illuminated solid angle and the illuminated area. In contrast to the luminous flux, however, the illuminance cannot be specified bindingly for every light source, as it depends on the specific room and application situation. The light intensity in candela is problematic and is only specified for lamps that emit directed light. Light sources can only be compared on the basis of illuminance or light intensity if the room situation, the angle of radiation of the light sources, etc. are known.



Luminous flux and the subjective perception of light

The same amount of light affects us very differently against light or dark backgrounds.

The brightness of light sources can generally be easily compared with one another using physical measured values ​​such as the luminous flux in lumens, although other factors such as the beam angle must also be taken into account. However, the actual perception of brightness is also influenced by a number of other factors. This is illustrated by the example in the picture above. There you can see very clearly that two scenes with the same equipment - luminaires with the same luminous flux and beam angle - appear different simply because of the color and texture of the background. Applied to our home lighting, this means that a luminaire or lamp with 1000 lumens is perceived as more powerful in a bright environment than in an environment with muted and dark colors. Light surfaces simply reflect the light better than dark and especially black surfaces. The latter virtually swallow the light and thus diminish our impression of the brightness of a room.


How well a light source can display colors affects our subjective perception of light.

In addition, the light spectrum and color rendering (CRI) of a light source play a decisive role in our perception of brightness. The light spectrum describes the color range that a light source covers. A complete light spectrum covers all three basic colors red, blue and yellow and thus makes a significant contribution to the color rendering of a lamp or luminaire. The latter provides information about how lifelike a light source represents colors and contours. A low color rendering index and an uneven light spectrum mean that we perceive colors as pale, which makes us judge the brightness of a light source to be darker. This also applies if two lamps, viewed objectively, emit the same amount of light. A 75 watt lamp with very good color rendering and a full light spectrum is always perceived as brighter than a typical fluorescent lamp with a comparable amount of light. The reason for this is that the latter emits light with a high proportion of blue, which also has a negative impact on the color rendering value.




This is how 1000 lumens work with a color rendering of Ra = 97.

So let's be clear: The specification of the luminous flux in lumens is a suitable benchmark in order to counteract the omission of the wattage as a benchmark. We can use the lumen values ​​to determine which light source is suitable as a replacement for our example with the 75 watt incandescent lamp. However, the supposedly exact measured values ​​cannot be easily converted into a brightness perception, since both the beam angle and the design of the luminaire or lamp influence the light impression. Ultimately, the color rendering as well as the colourfulness and texture of the background also shape our subjective perception of light.





Do you have any questions about your specific room situation? Are you unsure which light source you should replace your 75 W incandescent lamp with in order to achieve a similar brightness impression? Write to us, we will be happy to help you. Our colleagues from lighting planning will be happy to support you in finding the best light for your property.


Filed under guide, light quality
Tagged LED, luminous flux, lumen, room light.