directly adaptation and indirectly adaptation
When a person suddenly enters the dark place in a bright environment for a long time, he can't see anything at first. After a certain period of time, the visual sensitivity gradually increases, and the object in the dark can be gradually seen. This phenomenon is called dark adaptation (dark). Adaptation).
On the contrary, when a person suddenly enters the bright place in the dark for a long time, he initially feels a dazzling light, can not see the object, and only waits for a moment to restore the vision, which is called light adaptation.
In theory, dark adaptation is the process by which the human eye is gradually more sensitive to light in the dark. Generally, in the first 7 minutes after entering the dark, the threshold of the human eye's perceived light appears to decrease significantly, and then there is a more obvious drop again; about 25-30 minutes into the dark, the threshold drops to the lowest point. And stabilized in this state.
According to the analysis, the first stage of dark adaptation is mainly related to the increased synthesis of visual pigment in the cone; the second stage, the main stage of dark adaptation, is related to the enhanced synthesis of rhodopsin in rod cells.
The process of adapting is very fast, usually completed in a few seconds. The mechanism is that the rod cells accumulate a large amount of rhodopsin in the dark, and rapidly decompose when entering the bright spot when encountering strong light, thus producing a dazzling light sensation. Only after more rod pigments are rapidly decomposed, the cone pigments that are less sensitive to light can be sensitized in bright places to restore vision.
Professional "ethics" of lighting planning
Then the question is coming. What is the "ethics" of lighting planning? Reflected in professionalism, give a typical example:
Just imagine what is the range of outdoor illumination usually achieved? Up to 100,000lx on a sunny day, theater or cinema? If the safety lighting is only turned on more than 10lx, we assume that the outdoor is 10,000lx, and the audience walks into the 10lx theater room, during which the eyes are exposed to 1000 times the difference in illuminance levels.
From the theory of dark adaptation, the difference of the illuminance level of 1000:1 is adapted, and the average person may have to go through 15 minutes or even longer.
So what should a good lighting designer do in this case?
A good lighting designer should judge how the lighting route, the entrance, the hallway, the aisle, the corridor, etc., where the audience walks from the outdoor into the theater room, how to illuminate different levels of illumination at different locations, and use different illumination transitions. Help the audience to gradually build visual comfort.
For the above theater/theater examples, the light and darkness we are talking about is only a matter of comfort, but in some cases, the issue of security is related to security issues, such as tunnel lighting:
Therefore, in addition to understanding the meaning of different illuminance values, it is more important to understand the visual effects of light and darkness on people. This should be said to be the professional ethics of lighting designers.