What are the exposure modes of the camera and what are their functions? How to choose the metering mode of the camera, how to adjust the exposure compensation, how to quickly grasp whether the exposure is correct.
Aperture, shutter and sensitivity. We said that these three influence each other, but sometimes it is impossible for us to adjust the three parameters in real time. Even if we use manual exposure (M file), we will not adjust all the parameters every moment. We need the camera’s automatic exposure mode, and some parameters are controlled by the camera, which frees the photographer to focus on shooting creation instead of parameter adjustment.
The camera has four core exposure modes: aperture priority (A file), shutter priority (S file/T v file), programmed auto (P file) and manual mode (M file).
The so-called aperture priority refers to the priority calculation based on the aperture value. We first manually set the sensitivity and aperture, and the camera automatically determines the shutter speed based on these two parameters.
Aperture priority is suitable for most daily shooting environments, because we can freely control the aperture, so that we can control the depth of field according to our needs. For example, if we need to take portraits, we can increase the aperture to get a good blur effect. If we need to shoot landscapes, we use a small aperture, so that we can get a larger range of depth of field. If we need a long exposure, we need to adjust the small aperture while using a low sensitivity, such as ISO 100, to get a longer exposure time.
Going back to the exposure itself, using the A file, we control the aperture, and the camera automatically calculates the shutter speed. Therefore, the shutter speed does not actually need us to set. But if we need to pay attention to the shutter speed can not be too slow, if it is too slow, we need to use a tripod for stable shooting, otherwise the picture will be blurred.
The second gear is shutter priority, which is S gear or Tv gear. In this gear, our core control option is shutter speed. We first set the shutter speed, then select the sensitivity, the aperture is automatically set by the body.
Shutter priority is suitable for taking photos that require speed, such as sports, daily snapshots, etc. We can set the shutter speed as needed and let the camera automatically select the aperture.
It is worth noting that in these two modes, although our main adjustment parameter is aperture or shutter, the sensitivity also needs to be manually set. Of course, if the environment changes complex, we can also use the automatic sensitivity, that is, ISO AUTO, but we still need to always pay attention to whether the sensitivity meets the requirements, the focus is to focus on whether the sensitivity is too high, affecting the image quality; or the sensitivity has reached The upper limit causes the picture to be too dark.
The program priority is P file, but P file is not automatic mode. Many friends will confuse P file with AUTO file. In the P file, the sensitivity is still manually set by us (auto sensitivity can also be used), but the camera automatically determines the aperture and shutter speed. P file is more suitable for shooting complex environments, such as stage performance environment, fast changing environment.
The last exposure mode is M file, which is manual exposure mode. In this mode, the user freely controls all parameters, which is the most free type of shooting. If we shoot landscapes, long exposures, studio portraits, starry sky, etc., we generally use M files.
Let’s talk about the metering mode. Camera metering modes are generally divided into three types: evaluative metering or global metering, center-weighted metering and spot metering.
The principle of camera metering is based on the light. The camera removes the color from the image and only retains the brightness information. The camera’s automatic metering is to accurately record the measured part as 18% neutral gray. It is the correct exposure that the camera thinks.
The three metering modes are not difficult to understand. The so-called global metering or evaluative metering is to calculate the average value based on the entire screen portion to obtain the exposure parameters. This metering mode is suitable for landscape shooting and large scene shooting.
Spot metering is calculated based on the selected “point”, which is a relatively small area. Generally suitable for high light ratio shooting to meter the subject, such as portrait shooting. The center-focused metering can be understood as using a relatively small area in the center area for metering. This is the case for many old film machine metering. Compared with spot metering, the calculation area is larger and it is also suitable for large light ratios. Shooting that requires precise exposure of a specific area.
We have to deal with the three metering modes correctly in order to get the ideal exposure photos. If the camera’s automatic metering cannot meet the requirements, we also need to resort to exposure compensation.
The so-called exposure compensation is to artificially predict the light to adjust the exposure brightness. The exposure compensation button is generally written as EV, expressed in steps, generally we use 1/3 gear, or 1/2 gear to describe. For example, the exposure compensation of +1EV is to double the exposure, and -1EV is to reduce the brightness by one time.
In the M file, the exposure is adjusted manually by the photographer, so the exposure compensation does not work.
Finally, let’s talk about how to intuitively feel whether the exposure is correct. First, observe whether the highlights and shadows overflow. For digital cameras, a slight underexposure is acceptable, but the highlight overflow is hard to recover, so we prioritize shooting during the day to ensure accurate exposure of the highlights. We can use the camera’s highlight overflow tips, but a better way is to use the histogram.
Camera playback can directly view the histogram. In the ideal state, the histogram should be concentrated in the center area, and the two ends gradually decrease, and stop after reaching the two ends of the coordinate without overflow.
But under normal circumstances, we will not be in such an ideal state. We must first ensure that there is no overflow in the highlight part, that is, on the right side of the histogram. Of course, this depends on the situation. For example, when shooting a city at night, the lights will inevitably overflow. We can accept these.
In addition, the visual focus of the camera, that is, the highest part of the histogram, should be distributed as far as possible in the central area of the histogram. If the histogram is to the left or right, it means that the photo may be overexposed or underexposed, and you need to pay attention.
To learn metering, we must first understand the relationship between aperture, shutter and sensitivity. Furthermore, it is to learn how to use the camera’s existing automatic metering system to determine the exposure value we need as accurately as possible.