In our daily life, we will see all kinds of color objects. The color of the filter also includes red, orange, yellow, green, blue, purple and other colors. So what determines the color of the optical filter?
Optical filter is widely used in photography because of its great effect. Why is the main scene always so prominent in landscape paintings taken by some photographers? How is it done? That is, a filter is used. For example, if you want to take a picture of a yellow flower with the background of blue sky and green leaves, you can't highlight the theme of "yellow flower" if you take the picture as usual, because the image of yellow flower is not outstanding enough. However, if a yellow filter is put in front of the lens to block the green light from some green leaves and blue light from the blue sky, and let the yellow light from the yellow flower pass through in large quantities, the yellow flower will be very obvious, highlighting the theme of "yellow flower".
We need to understand the principle of light first. The principle of light irradiation on transparent and opaque objects is different.
1. The color of a transparent object is determined by the chromatic light it transmits. The color of a transparent object such as glass is determined by the chromatic light it transmits, and a transparent object can transmit the same chromatic light as itself.
For example, let white light through the blue glass, in addition to blue light, other color light can not pass through the glass smoothly, so we see the glass will appear blue. If a transparent object can let all the colored light pass through, then the bright object will look colorless.
2. The color of an opaque object is determined by the colored light it reflects
The color of opaque objects such as tables and walls is determined by the color light they reflect, while opaque objects mainly reflect the color light of the same color as themselves.
For example, let the white light shine on the blue object, the seven colors of red, orange, yellow, green, blue, indigo and purple in the white light will be absorbed by the blue object, only the blue light can not be absorbed and reflected back, so we can see that the object is blue. But if red light is used to irradiate the blue object, because the red light is absorbed by the blue object, we can't see the reflected light, so the blue object is black. The same is true for other opaque objects.
In addition, a white opaque object can reflect all colors of light, so no matter what color of light shines on a white opaque object, we can see what color it is. Black opaque objects almost do not reflect any color light, so any color light on its surface, we will be black because we can not see the reflected color light.