Basic theoretical knowledge of photography

What are the basic theoretical knowledge of photography? Mastering the basic knowledge of photography will make the photography process more handy. Here, I have compiled the basic theoretical knowledge of photography for your reference!

1, depth of field

When shooting, the process of adjusting the camera lens to make the scene at a certain distance from the camera clearly image is called focusing, and the point where the scene is located is called focusing, because? Is that clear? It is not an absolute concept, so the imaging of the scene can be very clear within a certain distance before and after the key point. The sum of the front and back ranges is called the depth of field, which means that as long as the scenery in this range is clearly photographed.

The depth of field, the first step, is related to the focal length of the lens. The lens with long focal length has small depth of field, while the lens with short focal length has large depth of field. Secondly, the depth of field is related to the aperture. The smaller the aperture (the larger the numerical value, for example, the aperture of f 16 is smaller than f 1 1), the greater the depth of field. The larger the aperture (the smaller the value, for example, the aperture of f2.8 is larger than that of f5.6), the smaller the depth of field. Secondly, the foreground depth of field is smaller than the back depth of field, that is, after accurate focusing, the scene in front of the focus can be clearly imaged, while the scene behind the focus 1 is clear.

2, focal length:

The lens of the camera is 1 lens. When the parallel light passes through the lens, it will converge to 1 point, which is called the focal point, and the distance from the focal point to the center of the lens is called the focal length. A lens with a fixed focal length, that is, a fixed focus lens; The lens whose focal length can be adjusted and changed is a zoom lens. In the field of photography, the focal length mainly reflects the lens angle. For the traditional 135 camera, the lens of about 50mm is close to the human eye and does not deform when shooting, so it is called a standard lens, generally covering the range of 40-70mm, 18-40mm is called a wide-angle or short-focus lens, 70- 135mm is called a medium-focus lens, and 135mm is called a medium-focus lens. The CCD of a digital camera is generally much smaller than that of 135 film, so the focal length of a lens with the same viewing angle is much shorter. For example, for a digital camera using a 0.33”CCD, when a lens of about 13mm is used, its viewing angle is equivalent to the standard lens of a 50 mm 135 camera ... Because the CCD specifications and models adopted by digital camera manufacturers are different, everyone adopts it. Equivalent to the focal length of a 35mm camera (i.e. 135 camera)? Statement.

3. hyperfocal distance

Because the depth of field behind the lens is relatively large, the distance that people can clearly image after focusing is called hyperfocal distance. Fool cameras generally use hyperfocal distance, which makes use of the feature that the scene can be clearly imaged at a certain distance with a short-focus lens, omitting the focusing function. Therefore, generally, low-grade fool cameras may be able to focus automatically, just using hyperfocal distance. As mentioned earlier? Is that clear? It is not an absolute concept, and the scenery in hyperfocal distance is not really clearly imaged. Because there is no focus on the key point, the imaging blur is affirmative, but the degree of blur is generally acceptable. This is the causal relationship that the negative film taken by a fool's camera can't be enlarged too much.

4. autofocus

There are several different ways of autofocus, which can be divided into active and passive according to the main control principle.

Active autofocus sends a beam of light (usually infrared) through the camera, determines the distance of the object according to the reflected light signal, and then automatically adjusts the lens to complete autofocus. This is the earliest developed autofocus method, which is relatively easy to complete, fast in response and low in cost, and is mostly used for mid-range fool cameras. This method has limited precision and is easy to lose focus. For example, when there is a reflector such as glass in front of the object, the camera may not be able to distinguish it correctly.

Passive focusing has a bionic taste, that is, it is more accurate to judge whether it has been focused by analyzing the imaging of an object, but it is difficult to focus accurately in low illumination because of its complex technology and high cost, and it is mostly used in high-end professional cameras. Some highly intelligent cameras can also lock moving objects and even control the focus with their eyes.

5. Automatic exposure

Automatic exposure means that the camera automatically determines the exposure according to the light conditions.

There are two basic photometry: incidence and reflection. The incident type is to determine the exposure combination by measuring the brightness of light shining on the camera, which is a simple and rough grasp, and is mostly used in low-end cameras. Reflection method is an ideal method to determine the exposure combination by measuring the actual brightness of the subject, that is, the brightness of the image.

From the perspective of metering methods, it can be divided into spot metering automatic exposure, center focusing automatic exposure, multi-point balance automatic exposure and so on. , each with its own advantages and disadvantages, is suitable for different lighting conditions or shooting purposes.

From the process of mastering, it can be divided into aperture priority, shutter priority, mixed priority, program mastery and predetermined mode. As the name implies, aperture priority is to determine the aperture used first, and the camera determines the appropriate shutter speed according to the calculated exposure. This method is suitable for places that need a predetermined depth of field or adjust the light ratio with a flash; Speed priority is to determine the shutter speed first and let the camera choose the appropriate aperture size to shoot moving objects; Mixed priority is to make up for the deficiency of single priority by first determining the range of aperture or shutter, and then determining the exposure combination by the camera; Program mastery is to expose the camera according to the pre-programmed mastery program; The preset mode is that the inventor preset reasonable exposure parameters for shooting according to several different and frequently seen light conditions, generally including: night scene, landscape, portrait, sports, etc.

6, red eye

It refers to the phenomenon that red spots appear in the photographer's eyes due to the reflection of blood vessels and veins in the fundus of the subject when shooting a portrait with a flash.

7, white balance

Because of the different spectral characteristics under different lighting conditions, most of the photos taken will have color deviation, such as blue under fluorescent light and yellow under incandescent light. In order to eliminate or reduce this color shift, digital cameras and video cameras can adjust the color settings according to different lighting conditions, so that the color of photos is as undistorted as possible and the color can be restored to normal. Because this adjustment is mostly based on white, it is called white balance.

Types of lamps

The basic direction of light is determined by the position of the camera, which can be divided into the following categories according to the direction of the light source:

1, positive light

The photographer's back to the sun, that is, the light from the back of the camera, is also called shun guang. Because all parts of the subject are bathed in direct light, there is light everywhere in the part facing the camera, resulting in an image lacking tone levels. It may not look good to pat your face with positive light, especially with high positive light.

2. Front side lights

The front light, also known as oblique light, is projected to the left and right sides of the scene and camera at a horizontal angle of 45 degrees. This light appears at 9: 00 am, 10 and 3: 00 pm. This kind of light is more in line with people's visual habits in daily life. Illuminated scenery, the projection falls on the inclined side, which has obvious difference between light and shade, and can better reflect the texture of the scenery. The 45-degree side light can be arranged between light and shadow, which makes the scenery colorful, highlights the deeper level and has the benefit of three-dimensional effect. In particular, it can show the texture of the appearance structure in detail.

3. Indirect explanation

Side light, that is, light from the left or right side of the scene, forms a 90-degree horizontal angle with the scene and the camera. This kind of light can produce a strong contrast. The shadow is slender and expressive, and the appearance structure is very clear. Every tiny bump has a clear shadow. The use of sidelight photography can produce a stronger modeling effect. In figure photography, sidelights are often used to reflect the specific thoughts of figures. Sometimes sidelights are also used as decorative lights to highlight a certain part or detail of the picture.

4. Backlighting

Backlight refers to the light coming from the opposite direction of the camera. White light outlines the edge of the scene and creates a sense of depth. Shooting the exterior and foreground with backlight can make the picture crystal clear, fresh in color and full of vitality. Reflecting things in the morning with backlight can enrich the color of the scene. With backlight, the subject will show a dark outline in front of a bright background. This image of Gao Fancha is both concise and expressive.

5. dome light

The top light, that is, the light from the top, forms a vertical angle of about 90 degrees with the scene and camera. In this light, the head, forehead and nose of the character are very bright, and the lower eye socket, cheeks and nose are completely in the shadow, forming an unusually unique shape. Therefore, it is generally avoided to shoot people with this light.