Table of Contents
Moderate Exposure
Load the film into the camera, adjust the focus, and press the shutter button to shoot. When the shutter button is pressed, the shutter of the camera is opened, and the silver halide coated on the film is irradiated by light and changes, resulting in a latent image. This process is called exposure.
The camera can control the amount of light that enters the camera, that is, how much exposure is made. By judging the light and dark conditions of the scene, adjusting the amount of light entering the lens, and then accurately imaging the film on the film, it is a moderate exposure.
The meaning of moderate exposure is to form an image with proper density, clear layers, and accurate color reproduction in light and dark parts on the negative. Overexposure and underexposure can result in images that are too bright or too dark and lose detail and depth. Therefore, proper exposure is a very important part of photography.
Metering
Metering is to test the exposure of the scene to be shot to determine a moderate exposure value. When metering, it is best to use the help of an instrument, that is, the metering device to be introduced below.
1. Type of metering device
The types of light metering devices are generally divided into two categories, one is the in-camera light metering system, and the other is the light meter that can be used alone.
There are many types of light meters: incident, reflective, and spot side light meters. The display of the light meter is either analog or digital.
In-camera metering systems are: pointer type, light-up type and exposure indicator type.
2. Metering method
Determining the correct exposure is actually measuring the unknown variables, and combining the measured numbers with the information already in the light meter and processing them together to arrive at a set of optimal speeds and apertures that can be used directly on the camera. There are two main types of light metering: incident light metering and reflective light metering. Detailed descriptions are given below.
(1) Incident metering
Incident metering is to point the meter at the camera from the position of the subject. This method mainly measures the intensity of light, and does not consider the reflection of the subject at all. Obviously, metering from the subject’s position is only necessary when the lighting conditions vary greatly within the scope of the shot.
If artificial lighting is used at close range, the light will decrease significantly with increasing distance, so the correct intensity of the light must be measured from the position of the subject. When shooting outdoors in sunlight, always meter close to the camera.
Since incident light meters measure light that is projected on a flat surface, the light receiving angle of the light meter must be large enough to cover a 180-degree range. To do this, add a spherical diffuser to the meter’s aperture. The numbers thus measured are based on the average reflectivity of the subject of 17%.
For objects with high contrast, certain corrections must be made. Negatives should be exposed slightly more than the light meter shows, and reversal films should be slightly less exposed. Since this method of metering cannot perform selective metering and spot metering, in order to achieve good results, some estimation work must be done, and some experience must be used.
If the light is difficult to measure, it is usually necessary to measure the reflected light again in order to compare it with the number measured for the incident light. If the difference between the two is too great, you should find out the reason for the difference and correct the exposure accordingly.
2) Reflective metering
When metering in this way, always point the meter from the position of the camera towards the subject. For accurate results, the metering angle of the light meter and the angle of view of the lens used should be roughly the same. If the metering angle greatly exceeds the angle of view of the lens, the meter should be placed closer to the subject, so that the field of view of the meter is roughly the same as that of the lens.
In reflective metering, the light meter shows the average reflected light from the subject. At the same time, it also measures all other reflected light within the metering angle.
As long as the measurements of the strongest highlights and darkest shadows are not too different from the average measurements of the focal points of the entire scene, this metering method will always provide an accurate exposure value. If there are small areas of extreme light or darkness in the scene, the overall average measured must be corrected. The degree of correction depends on the type of film used and how important these extremely bright or dark parts are on the frame.
3. Types of in-camera metering systems
The camera’s internal metering system measures reflected light, but different cameras have unique metering modes.
(1) Average metering
Average metering is the most widely used metering mode that cameras basically have. That is, all areas in the viewfinder are the range of light metering, and the camera measures an average value according to the light level of all the scenes.
This metering method is relatively simple. The disadvantage is that if the measured scene has areas with very large differences in tonal levels, the average metering will not be able to distinguish them very well. Still can only be metered according to the average mode, which can easily lead to exposure errors.
(2) Center-weighted metering (or simply: center-averaged metering)
Center-average metering is the most widely used metering mode. Almost all camera manufacturers use center average metering as the camera’s default metering method.
The central average metering is mainly considering that the general photographer is accustomed to placing the subject, that is, the thing that needs accurate exposure, in the middle of the viewfinder, so this part of the shooting content is the most important. Therefore, the sensory elements responsible for metering will organically separate the overall metering value of the camera. The metering data in the central part occupies most of the proportions, while the metering data outside the center of the screen is used as a small proportion to play an auxiliary role in metering.
The camera’s photometric data is obtained by the ratio of the weighted average of these two grid values by the camera’s processor. For example, Nikon cameras use center-weighted average metering. The central part of the Nikon camera accounts for 75% of the entire metering ratio (this ratio varies from brand to brand), and the metering data from other non-central parts that gradually extend to the edge accounts for 25% of the ratio.
Center-weighted metering is a very useful and widely used metering mode for most shooting situations. But if the subject you need to shoot is not in the center of the frame or if you’re shooting in backlit conditions, center-weighted metering won’t work.
Center-weighted metering is a traditional metering method. The metering algorithm of most cameras pays attention to about 2/3 of the center of the screen, and also gives some consideration to the surrounding area. For photographers who are accustomed to using center-weighted metering, it is easier to control the effect with this method than with multi-zone evaluative metering.
(3) Partial metering (or called: central partial metering)
Center partial metering and center average metering are two different metering methods. Center average metering is a metering method in which the center area is the main area and other areas are auxiliary. The central part of the metering is only a central area of the screen for metering, the metering range is about 3% to 12% for metering.
The central part metering mode is suitable for some scenes with more complicated lighting, and more accurate exposure is required at this time. Using central partial metering can result in a photo with an accurate exposure of the subject.
The central part metering can be applied to some special harsh shooting environments, which can ensure that the camera processor can calculate the exposure required for the main object part in the center of the screen. This mode is most suitable for scenes such as stages, performances, and backlighting. However, due to the rise of split metering (matrix metering) mode, this mode has gradually appeared in cameras less and less.
This allows cameras without spot metering to reduce the effect of light on the subject when taking pictures in some complex lighting conditions.
Partial metering method is to meter a certain part of the screen. This metering method is most suitable when the subject and the background have a strong contrast between light and dark, and the subject does not occupy a large proportion of the screen. In this case, partial metering is more accurate than the first and second metering methods. Unlike the spot metering method, which requires a certain amount of metering experience because the metering spot is too narrow, it is not easy to make mistakes.
(4) Multi-area metering (or split metering)
Multi-area metering modes are mainly matrix and cellular. The matrix metering method is unique to Nikon automatic cameras, while the cellular metering method is set for Minolta automatic cameras.
Split metering is a relatively new metering technology that has been around for less than 20 years. The biggest difference between split metering and center-weighted metering is that split metering divides the framing screen into several metering areas. After each area is independently metered, the overall exposure value is integrated and weighted to calculate an overall exposure value.
The split metering introduced at the beginning generally has a relatively small number of splits. They were analyzed independently after photometry. The difference is only in the distribution of the metering area or the analysis algorithm. This is not only dependent on the hardware performance of the camera itself, but also closely related to the processing power of the camera and data analysis algorithms.
Multi-zone evaluative metering is the most advanced intelligent metering method at present. It is a judgment that simulates the human brain for uniform or non-uniform lighting conditions that are often encountered when shooting. Even people who are not familiar with metering can generally get a more accurate exposure film in this way.
This mode is more suitable for photos of large scenes, such as landscapes, group photos, etc. It works best when shooting scenes with more positive light sources and more uniform lighting. It has become the most commonly used metering method for many photographers and photography enthusiasts.
(5) Spot metering and multi-spot metering
Spot metering only accurately measures the light in a small area, and the brightness of the scene outside the area has no effect on the metering. Therefore, the metering accuracy is very high. Its purpose is mainly to meter light in a specific small area in the distance. Mastering this metering method requires the photographer to have a certain understanding of the spot measurement characteristics of the camera used, and to know how to select a metering point with a reflectivity of about 18%. Or exposure compensation can be made empirically for metering points above or below 18% reflectivity. The spot measurement method is mainly used by professional photographers or people who have a good understanding of photography techniques. Improper use of the point measurement method will cause confusion.
Multi-spot metering is also known as “zone integrated metering”. It is an advanced metering system. This light metering system uses multiple light metering elements, each of which measures light to a predetermined area of the screen, and then inputs the respective light metering data into the camera’s microcomputer, which is calculated by the computer to obtain accurate automatic exposure data.
Applicable shooting purposes: stage photography, personal art photos, news feature photos, etc.
(To Be Continued)