Fundamentals of photography-light, color and image

In the dark, we can't see the shape and color of the objects around us, because there is no light. Under the same light conditions, we will see that the same scenery has different colors, which is caused by the different degrees of light absorption and reflection on the surface of the object. The light reflected by the object is different, and the eyes will see different colors.

The production of color is the result of light acting on human vision and brain, which is a kind of visual perception. It can be said that light is colored, and no light is colorless.

1. Light is the material basis of color generation and the premise of human vision.

2. Cone cells in human retina are the physiological basis of color vision.

3. Color vision adaptation is a physiological phenomenon when people observe colors.

(1) Complete adaptation (color vision protection)

When we observe the external scenery, even if the lighting conditions or observation conditions change, it will not affect the observer's subjective judgment of color.

(2) local adaptation

When the eyes stare at a strongly colored object for a long time and suddenly turn to a colored or colorless plane with strong and uniform illumination, you can see a colored afterimage.

(3) lateral adaptation

In front of a bright background, the color of the object will darken; Before the dark background, the color of the object will brighten. If an object is surrounded by a colored background, the color of the object will change to a complementary color close to the background color.

Colorless is a colorless color, usually black, white and gray.

Some objects do not selectively absorb and reflect the spectral components of the light source, but equally absorb or reflect various spectral components. These objects look colorless, so they are generally called colorless objects.

Achromatic plays a very positive role in color configuration and visual effect. With any color configuration, it is very harmonious and can receive satisfactory color effects.

The subject appears in various colors because of the light. Under the same light source, each object absorbs and reflects light differently, so objects appear different colors. At the same time, for the same object, although its absorption and reflection are the same, it will see different colors under different light sources.

In the process of photography, you should know the color of the object and the color of the light source. Please note the following points.

Properties of (1) projected light. In order to better represent the inherent color of the subject, we should try to use scattered light for illumination when choosing the properties of illumination light.

② the intensity of light. In order to make the inherent color of the subject show well, the intensity of the projected light should be appropriate, neither too strong nor too weak.

③ The surface structure of the object. The inherent colors of spherical surface and glossy surface are not as saturated as rough surface and plane.

(4) the distance of the object. The farther the object is from the viewer, the more unsaturated the color is, with some blue-green tones, and its inherent color is also weakened.

As can be seen from the above points, we should show that the inherent color of the subject should be saturated and bright, and the light should not be too hard or too strong. Moreover, if you want to express the color of smooth surfaces and spherical objects, you should try to use soft indirect light, such as scattered light, to avoid reflection on their surfaces.

The color of the environment is called "environmental color", which is mainly reflected in the shadow of the subject. When there are too many colors around the object, it is easy for the object to be biased towards which color.

Color temperature is the symbol of the color composition of light source, and the unit of measurement of color temperature is Kelvin. The higher the color temperature, the bluer the light. The lower the color temperature, the redder the light. In photography, the color temperature only refers to the different proportions of red and blue light contained in the light source, which has nothing to do with the actual temperature.

The color temperature of the light source will affect the effect of the photo and make the color of the photo deviate. When taking pictures, you can adjust the white balance of the camera to make the color return to normal.

The three primary colors of light are mixed in different proportions, and almost all colors of light in nature can be obtained. The equal mixing of three primary colors produces white light or gray light, which is called the principle of color light additive method. The three primary colors of pigments are cyan, magenta and Huang San, and the same amount of pigments are mixed to produce black, which is the so-called pigment subtraction principle.

1. Tone (color)

Hue is the most basic feature of color, refers to the difference between color and color, and is the name and appearance of various colors, such as red, green, blue and cyan.

2. Brightness (brightness)

Brightness is the brightness and depth of a color. It can help us to further understand the relationship between light and shade and the three-dimensional space of the subject, distinguish the changes of light and shade of various colors, and facilitate us to use colors properly when shooting high-profile or low-key color photos.

3. Purity (saturation)

Purity refers to the brightness of a color, which depends on the ratio of colored components to achromatic components contained in a color. The greater the color component, the greater the saturation; The larger the achromatic component (black, white and gray), the smaller the saturation. In photography, for a specific color, its saturation is the highest only when the exposure is correct; Overexposure or underexposure will reduce the saturation of color.

Red-joy, enthusiasm, courage, enthusiasm, liveliness, excitement, anger, cruelty, strength, firmness and sincerity;

Orange-cheerful, luxurious, positive, energetic and willful;

Yellow-sunny, noble, bright, bright, cheerful, developing, peaceful, victorious, frivolous and indifferent.

Green-life, liveliness, peace, hope, freshness, comfort, calmness, stability, ideal, innocence, softness, rust and mildew;

Blue-sublime, eternal, cold and cheerless, quiet, quiet, calm, profound, negative, long-lasting, thoughtful, true and calm;

Purple-beautiful, mysterious, uneasy, eternal, noble, gentle, elegant and reckless.

Black-serious, horrible, mysterious, lonely, sad, desperate, dark, twisted, gloomy, secretive and profound;

White-bright, pure, simple, frank, happy, bright, peaceful, sacred, clear, fragile, sad and noble.

Image files are usually stored in JPEG, TIFF, RAW, BMP, GIF, PNG and other formats.

RAW is the record of the original data after the CCD or CMOS of the camera converts the optical signal into an electrical signal. It just records and stores the image data without any processing inside the digital camera. RAW is an unprocessed and compressed format. For a 5-megapixel digital camera, a RAW file saves 5 million points of photosensitive data, so the file is very large, but it saves the original image coding data, which is very beneficial to the photographer's post-processing. Select "RAW+L" as the image quality setting of digital SLR camera, which can save both RAW images and JPEG images.

TIFF is a lossless compression format (the highest compression ratio is 2~3 times). This kind of compression is the compression of the file itself, that is, it records some repeated information in the file in a special way, and can completely restore the file, maintaining the original color and hierarchy. Advantages are good image quality and higher compatibility than RAW format, but it takes up a lot of space.

JPEG is a file compression format that can provide excellent image quality. The photos taken in JPEG format have been processed by the image processor inside the camera and can be released directly.

Bitmap image is also called "bitmap" and "pixel map", that is, the image is composed of colored squares, which is related to the resolution. The more pixels per unit area, the higher the resolution and the better the image effect. Bitmap images are composed of many points, and each point is called a "pixel". The disadvantage is that it will be distorted after amplification and the generated file will be large; The advantage is rich colors. Photos belong to bitmap images.

Vector graphics, also known as "vector graphics", are composed of curves described by mathematical methods, and their basic components are anchor points and paths. Drawing with CorelDRAW, Illustrator, FreeHand and other software has nothing to do with the resolution, and it is not distorted after amplification, and the generated file is small, with the disadvantage of single color. Vector images are mostly used in graphic design such as logo and poster.

Image resolution refers to the number of pixels contained in a unit length. The units of resolution are dots per inch (dpi), pixels per inch (ppi) and pixels per centimeter (ppc). Generally, the resolution of images used for printing should reach at least 300dpi, and the printed images below this value are not clear enough. If you print or spray paint, you only need 72dpi. The higher the resolution, the clearer the image, the larger the generated file, and the more memory and CPU processing time are needed in the work. Therefore, when making images, it is necessary to set appropriate resolutions for images of different quality. For example, the image resolution used for printout needs to be higher, and works that are only displayed on the screen (such as multimedia images or web images) can be lower.