Q: We usually say illuminance when designing, but when we evaluate the effect, we increase the brightness. How to understand the relationship between the two?
A: Before understanding the relationship between the two, we need to understand the conceptual difference between "illuminance" and "brightness":
Or we can explain it in a simpler and more intuitive way: brightness refers to the intensity of light that can be felt in the eyes of a person, and illuminance refers to the amount of light that is received by the illuminated surface.
These two can be based on the concept of physical hard indicators, the brightness is more focused on the degree of human feelings, we often say that a place is very bright and will not say very "photo", that is, people's feelings, refers to this place After the item is illuminated, there is relatively more light reflected into our eyes. Illumination refers to how much light falls on the surface of the object being illuminated.
Why do we use illuminance to measure the quality of lighting in a place?
Under the premise that the brightness value cannot be obtained very simply, we use the illumination to evaluate the lighting quality of the place.
Take the school as an example. We actually walked into the classroom to measure whether it met the standards of our study and class. What did we look at? It’s not how bright the lights are, but whether we look at the blackboards, desks, books are not bright enough, or will it be too glaring, what are the lights reflected in the eyes of the blackboard, desk, and books after being illuminated by the lights, In fact, those are the concept of brightness.
But there is a problem. The blackboard is black and frosted, the desk is yellow and smooth, and the textbook is white with both smooth and matte. Under the same illumination, the reflectivity of the above items is different. The brightness we see with the naked eye is naturally different.
Since brightness is the perception of the human eye, should we stipulate: "The brightness in the classroom should be 50cd/m2"? We push back according to the reflectivity of each object, so that the illumination on the blackboard should be 700lx, the illumination on the table should be 500lx, and the illumination on the textbook should be 300lx... Obviously, this will be more confusing.
We often say that space lighting design is the design of spatial brightness distribution, but it is obvious that in actual design, it is impossible to specify the brightness distribution of each object surface. It is very difficult to design and test.
Therefore, this is a case in which we obviously cannot measure the quality of lighting by specifying the brightness. We can only judge the amount of light obtained by the object under the premise of setting a general range of conditions to comprehensively judge the quality of lighting. .
This routine is a premise of exploration, including assuming that most of the books are white, the blackboard is black and frosted, the desk is yellowish, etc. They have a weighted average of reflectivity and usage routines. Under this convention, we can simply determine how much light they are exposed to by the light source to assess how comfortable we are for reading and writing.
Figure: A white wall whiteboard light-colored desk in Class A, students read white-printed books, which may be close to our current routine, we can meet the daily classroom, reading and writing needs with 300lx illumination. But in the extreme situation B classroom, using black walls (such as analogy in the dark red sound-absorbing panel wall in the cinema), blackboard, black desk, reading books are printed on black paper, then get the same classroom as in A classroom , reading, writing needs, perhaps to increase the illuminance standard to 500lx to get.
In fact, our national standards stipulate that, under the premise of satisfying seven reasons, the illuminance can be increased or lowered. For example, the person in this place is sensitive to the eye, which can be appropriately reduced.
When is the brightness measured?
Contrary to the above, brightness is used as a measure when it is easy to obtain luminance data. Give two examples:
First, the surface brightness of the luminaire. The surface brightness usually refers to the glare of the lamp. If a room has some lamps with high surface brightness, it will be very uncomfortable after entering, because there is light glare on it. In this case, the light is directed into the eye, and there is no reflection, so the illumination cannot be formed.
This data is available to luminaire manufacturers when doing professional optical inspections. The data is relatively easy to obtain, so we use it relatively more and will use it to measure the direct and indirect glare caused by a luminaire in space.
Second, Road Lighting. Unlike indoors, the relationship between road lighting and driving safety is particularly important. We know that we see whether things are bright or the contrast between light and dark is due to brightness, so road lighting should be measured by the brightness of the driver's viewing direction, but because the road surface material is relatively simple: asphalt or concrete, so the national standard There is also a system that is directly measured in terms of illuminance standards.
When calculating this brightness, there is a model that calculates the brightness data obtained by the observer (such as the driver). Because we know the reflectivity of the road clearly, whether you use asphalt or concrete and the brightness must be 1.0cd/m2, the designer can adjust the illumination on different pavement materials to achieve the same brightness standard. .
Figure: The asphalt pavement on the left side has a lower reflectivity than the right concrete pavement. The illumination with the same brightness standard will be slightly higher than the concrete.
Traffic Lights are traffic lights that command traffic and are generally made up of red lights,green lights and yellow lights.The red light means no traffic,the green light is allowed to pass,and the yellow light is a warning.
Traffic lights are divided into:light motor vehicles, no-motor vehicles lights,pedestrian signal lights,direction indicator lamp(arrow lights),driveway lights,flashing warning lights,road and rail light plane crossing.
Traffic Lights
Traffic Lights,Traffic Lights For Sale,Traffic Lights Word Search,Traffic Lights Invented
Jiangsu chengxu Electric Group Co., Ltd , https://www.chengxulighting.com