What are the characteristics of the light source for photography?

Natural light: mainly refers to sunlight with a color temperature of 5500K K, and the energy ratio of red, green and blue spectra of sunlight is basically the same, which is suitable for black and white panchromatic film or color film photography. The morning, noon and evening sunshine are different all the year round, which is caused by the different sunshine intensity caused by the changes of season, time, weather and geographical location.

Photographic sunlight: refers to the sunlight that shines 40 degrees above the horizontal line in a cloudless atmosphere, at which time the color temperature is 5500K, which is the standard sunlight and is most suitable for shooting sunlight color films. Therefore, the World Organization announced in 1983 that this is a new international standard for measuring the color reproducibility of camera lenses.

Skylight: also known as skylight or sunlight, it is a kind of natural light. Sunlight scatters to the ground through dust, water vapor and other media in our atmosphere. Objects illuminated by this light will not produce strong shadows. The brightness of skylight is lower than that of sunlight, but the color temperature is higher than that of sunlight.

Indoor natural light: the lighting conditions of indoor natural light are very different from those of outdoor natural light. Generally speaking, indoor natural light changes with the architectural structure of the room. This change includes sunlight or skylight projected from the outside and light reflected from four walls to illuminate the indoor scenery. As for the indoor brightness, it is determined by the number of windows, the reflective ability of walls, the distance of scenery near doors and windows and other factors. Pay attention to the above conditions when shooting.

Artificial light source: artificial light source refers to light. The artificial light sources commonly used in photography are: ordinary incandescent lamp, tungsten halogen lamp, metal halogen lamp, short arc xenon lamp and flash lamp.

Color temperature of light source: when the color of the light emitted by the light source is the same as that of the black body (refers to the fact that an object absorbs all the radiation falling on it without reflecting or transmitting under the radiation. When the blackbody continues to heat, the light emitted has a certain color, and its changing order is red-yellow-white-blue.) At a certain temperature, this temperature of the blackbody is called the color temperature of the light source, which is called absolute color temperature for short.

Temperature scale: the temperature scale refers to the temperature scale of K. The color temperature is determined by Kelvin, so it is called the temperature scale of K. The application of color temperature in photography is to measure the composition of colors contained in light, not to measure the temperature of hot and cold in light. The temperature scale, that is, the standard unit of color temperature, is represented by "K".

Color temperature tolerance: color film has certain requirements for color temperature. Daylight color film is suitable for shooting in sunlight with a color temperature of about 5500K, but it has a certain color temperature tolerance, which is generally1000 K. Light color film is suitable for lighting with a color temperature of 3200K ~ 3400K, and its color temperature tolerance is 700 K. Within the tolerance range, shooting is allowed. It can be corrected when printing and playing color films. If these two types of color negative are photographed according to the required color temperature, the effect of taking color photos in the future will be better. The color temperature tolerance of color reversal film is small, so the color temperature of light source must be strictly controlled.