Introduction and classification of digital camera parameters

(Note: ISO is the abbreviation of International Organization for Standardization. ISO does not mean sensitivity, but quantification. )

Both traditional cameras and digital cameras have this setting, which is the size of the photosensitive capacity of film or CCD. The general ISO value of ordinary household film is 100, which is like a standard value. Below this value, you can basically achieve correct exposure in various occasions. It is suggested that novices can use this value to operate. If it is lower than 100, such as 50 or lower, the picture quality will be improved, and the picture will be more delicate, suitable for shooting portraits or still life scenes, and the layers are very rich. The influence of low sensitivity is that the exposure time is prolonged, so we have to enlarge the aperture or slow down the shutter to supplement the exposure to achieve the correct picture requirements. If the sensitivity value is higher than 100, such as 200,400 or higher, the graininess of the film picture will be enhanced and the CCD picture will produce noise. Its advantage is that you can choose a faster shutter speed or a smaller aperture to achieve correct exposure by reducing the amount of light. This method is more suitable for capturing moving scenes or dynamic scenes, and it can produce special effects if used reasonably. In a dark environment, it is also a good idea to improve the sensitivity value.

Aperture:

The luminous flux of the lens has the function of controlling the aperture. Generally, the larger the lens aperture (the smaller the F value), the more light passes through. The characteristic of large aperture is that it can obtain a shallow depth of field, that is, the subject is clear and the foreground background is blurred. This method is often used in portrait photography to highlight the theme. Of course, the focus under large aperture must be accurate, otherwise the shallow depth of field can easily be illuminated as the deviation of focus. The smaller the aperture (the larger the f value), the less light passes through it, and the longer the depth of field can be obtained under a small aperture, which is more suitable for representing a wide range of clear landscapes or environments.

Shutter:

As the aperture changes, you can adjust the shutter speed to achieve the correct exposure. Shutter is the length of exposure time. For example, if your aperture is determined to be F8, then the faster the shutter, the less light will enter, and the slower the shutter, the more light will enter. Fast shutter can instantly condense motion on the negative or CCD, such as a gushing waterfall, and condense into crystal clear water drops in the sun. If you slow down the shutter speed, the subject will be clear, the crowd in the background will become a fuzzy movement effect, and the vividness of the picture will be enhanced.

Relationship between aperture and shutter:

After determining the correct exposure of the scene, different exposure combinations can be changed to achieve different effects. For example, the correct exposure value of a scene under ISO 100 is F8,1125, then you can choose F5.6, 1/250-F65438+. To control the expressive force of the picture, there is a common law "reciprocal rate" in photography-that is, to ensure correct exposure, you can enlarge the first aperture and raise the first shutter at the same time, or narrow the first aperture and lower the first shutter at the same time. This is a trade-off relationship. To enlarge or reduce several apertures, it is necessary to speed up or slow down several shutters accordingly. Only in this way can we maintain the correct total exposure and ensure the picture quality. The picture effect is achieved by constantly changing the combination of aperture and shutter. Of course, this reciprocity rate sometimes fails, such as shooting the starry sky on a moonlit night and other special environments. Here, it is not a simple reciprocity rate that can be solved. More depends on the photographer's experience and skills, which need to be summarized through practice.

Application of ISO value:

The ISO value can control the exposure. Usually, if the ISO value is increased by one step, the aperture can be reduced by one step, or the shutter can be accelerated by one step, and vice versa. This also needs to be adjusted according to the requirements of the picture effect. Of course, in general digital cameras, high ISO will bring higher stability and sensitivity, but it will inevitably reduce the imaging effect. For example, in the same sample taken by ISO64 and ISO200, ISO pictures are almost certainly cleaner and have much less noise. Therefore, people who use ordinary DC, in the state of poor light, suggest using tripod instead of blindly improving ISO to improve stability!

Aperture priority is to manually define the aperture size, and the camera will decide the shutter speed according to this aperture value. Because the aperture directly affects the depth of field, this mode is most widely used in ordinary shooting. When shooting portraits, we usually use large aperture and long focal length to blur the background and get a shallow depth of field, which can highlight the subject. At the same time, a larger aperture can also obtain a faster shutter value, thus improving the stability of hand-held shooting. When taking photos such as scenery, we often use a smaller aperture value, so that the range of depth of field is wider, which can make the distant and nearby scenery clear, which is also applicable when shooting night scenes. However, for lenses with poor quality, the picture quality will be affected to a certain extent when the aperture is fully open, and the lens with small aperture usually has better picture quality. Contrary to aperture priority, shutter priority is to manually define the shutter value of exposure, and the camera will determine the aperture size according to this shutter value. Set the camera dial to S, or set the exposure mode to S in the menu, which is the shutter priority function. Shutter priority is mostly used to shoot moving objects, such as sports, moving vehicles, waterfalls, flying objects, fireworks, water droplets and so on. Many friends find that when shooting moving objects, the subject is often blurred, mostly because the shutter speed is not fast enough. In this case, you can use the shutter priority mode, roughly determine a shutter value, and then shoot. And the motion of the object is generally regular, then the shutter value can also be roughly estimated. For example, the shutter speed for photographing pedestrians is only1125 seconds, while it takes11000 seconds for photographing falling water droplets.

The role of aperture control in shooting

Adjusting the aperture can control the depth of field of the subject. The larger the aperture, the smaller the depth of field (shallow), and the smaller the aperture, the greater the depth of field (deep).

Shooting with the large aperture of f2.8, we can see that the depth of field of the scene is very small, and it is clear until the plane of the first car is small, and the farther the car behind it is, the more obvious it is. If the photographer's goal is to blur the background with shallow depth of field and highlight the first car, then the performance goal can be achieved by setting the aperture.

When shooting portraits, in order to highlight people and reduce the influence of background clutter, you can use a large aperture to blur the background.

The aperture of f 1 1 can be seen clearly at the back of the car base.

If the goal of shooting performance is to clearly shoot far and near scenes, then the goal can be achieved with a smaller aperture setting. When the aperture is set to f32, the far and near scenes are very clear.

When shooting a scene, we can set a small aperture to achieve the purpose of performance, so as to have a clear performance of the near and far scenes.

The role of shutter control in shooting

At a faster shutter speed, the camera can freeze the instantaneous behavior. A slow shutter speed can record a motion track and make the photo full of motion.

Urban traffic speed is relatively slow. The shutter speed of 1/90 seconds above can freeze the moving vehicle into a stationary moment.

At the shutter speed of 1/4 seconds, it can record the short driving track of the vehicle and add some movement to the picture.

At the shutter speed of 2 seconds, the moving vehicle can only see some virtual shadows of the driving track.