Basic knowledge of photography theory

In daily life, due to the adjustment ability of eyes, we often ignore the color changes of some things around us. However, these changes can be faithfully recorded in your photos through digital cameras or films in photography. The following is the basic knowledge of photography theory that I have carefully arranged. Welcome to share.

Basic knowledge of photography theory

1. What kinds of filters are there for shooting?

A: You can use the "Shoot" filter to present various special effects. For example, if you shoot water or glass directly, the color of the photo will become dim because of the reflection on its surface. "PL (Polarization) Filter" can suppress surface reflection and make colors brighter. If you use it to shoot the blue sky or leaves, you can make the sky bluer and the leaves greener. In addition, there are "soft focus filters" that can make the whole photo brighter, and so on. It should be noted that the aperture of the filter must match the aperture of the lens. Therefore, when choosing a filter, it is necessary to confirm not only the type of the filter, but also its caliber.

2. Can the light intensity of the flash be adjusted?

A: There are two ways to adjust the brightness of the flash. One is to adjust the flash itself, and TTL photometry is a common means. Because this method is adjusted on the flash itself, it is effective no matter how the aperture is adjusted. So don't worry about being limited by the depth of field.

Another method is to adjust the light receiving amount by adjusting the aperture value and ISO sensitivity, which is an effective skill when using a flash lamp that cannot adjust the output power. In this case, although the amount of light emitted by the flash is certain, the appropriate exposure can be selected by adjusting the aperture value and ISO sensitivity to avoid the phenomenon of dead white and dead black. But because this is manual dimming, it needs to be readjusted every time the distance between the camera and the subject is adjusted. If the ISO sensitivity is improved, the effective distance of the flash can be extended.

3. What is the "flash index" of the flash?

A: The flash index is a numerical value indicating the luminous quantity (light intensity) of flash. The larger this value, the farther the flash can shine. In addition, the reach distance of the flash can be calculated by the values of flash index, F value (aperture) and ISO sensitivity. If "GN" is used to represent the flash index and "f" is used to represent the aperture, the calculation formula is as follows (unit meter): arrival distance =GN÷F×ISO/ 100. The flash index of the built-in flash installed in a general digital SLR camera is "12". When the ISO sensitivity is 100, the reach distance of F4 is 3m, and that of F5.6 is 2.1m.. When the ISO sensitivity is 200, the reach distance of F4 is 6m, and that of F5.6 is 4.2m, which is twice that of ISO sensitivity of 100.

But in most cases, the flash of digital SLR cameras automatically adjusts the output power, so few people will realize the existence of flash index. In addition, the shutter speed has no effect on the effective distance of the flash.

4. Is a range hood a must?

A: A hood is a must for photography. In order to take beautiful photos, the most important thing is to let only the light involved in imaging enter the lens. Using the hood can block the interference light from all directions to the lens, and only keep the light from the direction of the subject. In the process of shooting, if there is interference light entering the lens, it will cause confusion in the internal reflection of the lens, resulting in low contrast and unclear picture.

By the way, some lenses have small windows on the hood. When using a PL (polarization) filter that can suppress the reflection of the object surface, it is necessary to control the picture effect by rotating the PL (polarization) filter. At this time, if a range hood is installed, it will be very difficult to adjust the PL filter, and the small window on the range hood is designed to rotate the PL filter more conveniently in this case.

5. What's the difference between the front curtain synchronization of the flash and the Hou Lian synchronization?

Answer: Front curtain synchronization means that the front curtain is opened, the flash starts to illuminate the subject, and then the camera is exposed. Hou Lian synchronization means that when the curtain is opened, the flash will not flash first, but wait until the moment before the Hou Lian is closed to complete the exposure.

When shooting a still object, there is no motion track of the subject in the picture, so these two flashing methods have the same function, both of which are to ensure the correct exposure of the subject and background. However, when shooting a moving object with a low-speed shutter in the evening, at night or indoors, if the subject is still moving after the flash is flashed, it will leave a virtual shadow of the subject moving in front of the exposure position; However, if the Hou Lian is used for synchronous shooting, although the virtual shadow of the moving subject will still be photographed, the flash will flash before the Hou Lian is turned off, so the subject can be clearly photographed.

Basic theoretical knowledge of photography

1. Increase exposure compensation and shoot fair-skinned portraits.

Portrait photography, if you increase the exposure compensation of +0.3EV~+0.7EV, you can shoot beautiful human skin color. The method is to measure the exposure value of the skin (especially the spot metering method is more accurate), and then increase a certain EV value, which can make the skin look whiter.

The above is only for shooting beautiful women and children. If you want to photograph old people or people with dark brown skin, or people in mines or underground coal mines, you should make negative exposure compensation to make their skin look more saturated and deeper, so as to highlight their own age, race and professional characteristics.

2. Increase exposure compensation and shoot white clouds, white fog and snow scenes.

Shooting white clouds and fog scenes is different from ordinary landscape photography, and usually the pictures to be shot are high-profile types. Therefore, when shooting in evaluation metering mode, the picture may become gloomy, so it is necessary to measure the fog points in the picture and increase the exposure compensation appropriately.

The same problem exists in shooting snow scenes. Because the brightness of snow is very high, exposure according to the photometric value calculated by the camera itself will lead to underexposure, which will make the photographed snow gray. Therefore, exposure compensation function is generally used to correct exposure when shooting snow scenes. According to the proportion of snow in the picture, it is usually necessary to increase the exposure compensation of 1 to 2 blocks. The left side shows the beautiful scenery that can only be taken by adding exposure compensation.

3. Reduce exposure compensation to make the picture more colorful.

Exposure parameters have a great influence on the color of the picture. The more exposure, the brighter and lighter the color of the scene in the picture. On the other hand, if the exposure is insufficient, the color of the scene in the picture will appear dull and rich.

Therefore, on the basis of normal exposure, properly reducing the exposure compensation can make the color of the subject look richer.

If you shoot the blue sky, you can make the sky in the picture look bluer by reducing exposure compensation. If you shoot flowers, you can compensate by reducing the exposure, so that the colors of flowers in the picture look brighter.

4. Reduce the exposure compensation and take a simple picture with a dark background.

When shooting flowers, still life and other subjects, in order to make the picture more concise, we can use the spot metering mode to aim at the relatively bright area of the subject in the foreground for metering, so as to ensure the accurate exposure of the subject. Then, by compensating the negative exposure of the photo, the background becomes dark or even pure black due to underexposure, thus highlighting the subject in the foreground.

5. Emphasize the contour effect by reducing exposure compensation.

When shooting backlit works, exposure control can not only show the overall environment including details, but also treat the picture as a silhouette. The former needs to increase exposure compensation, while the latter needs to decrease exposure compensation.

In actual shooting, you can follow the following steps.

(1) Set an exposure compensation value, such as -2EV, according to the scene to be shot and the darkness of the silhouette to be reflected.

(2) aim at the details of bright clouds or water in the sky, so that this part can be correctly exposed in the picture and present certain details.

(3) Press AE-L/AF-L button to lock the exposure parameters.

(4) Move the camera to re-compose.

(5) Focus on the subject and press the shutter to complete the shooting task.

(6) Preview the photo, adjust the exposure compensation value according to the effect, and then shoot again until the satisfactory effect is obtained.

When shooting, you can also add atmosphere to the picture by setting the white balance to "cloudy" or "dark" mode.

6. Reduce the exposure compensation, so that the background becomes a prominent flower with darker tone.

When shooting flowers, if the subject is in front of the dark background, the exposure can be appropriately reduced by reducing the exposure compensation, and the background is shot in pure black, thus highlighting the subject in the foreground.

It should be noted that the spot metering mode should be adopted to measure the light in the relatively bright area of the subject in the foreground to ensure the accurate exposure of the subject.

When shooting, the set exposure compensation value depends on the area of dark background in the picture. The larger the area, the greater the exposure compensation value should be.