How to use the exposure meter?

The metering system in modern cameras has been very developed. Why do many photographers use hand-held exposure meters independent of cameras? Because (1) there are few cameras with perfect performance above medium film size, most cameras with large film size have no metering system. ⑵ Compared with the in-camera metering system, the hand-held exposure meter can have more sensitive and accurate metering performance, such as110 of the first aperture, which is more sensitive to low light. The measuring angle can also be very small, such as 1 degree, which is beyond the reach of the common cameras with "spot metering function" at present. ⑶ In some occasions, such as scenery, still life, products and model photography, it is not convenient to move the camera to measure light, but it is much easier to put the camera on a tripod and take an exposure meter to measure, think and judge. ⑷ The in-camera metering system can only measure reflected light, and the hand-held exposure meter can also measure incident light and flash.

Reflected light exposure meter

Exposure meters can be divided into two categories according to the different measured light, namely, reflected light exposure meters and incident light exposure meters. The reflected light exposure meter is used to measure the reflected light of the scene and measure the brightness. Camera built-in exposure meters all belong to this category. Some hand-held exposure meters can only measure reflected light, but now most hand-held exposure meters can measure reflected light and incident light respectively.

People who use the exposure meter must remember one of its basic principles: the result measured by the exposure meter is a medium gray tone on the final film or photo! The function of the exposure meter is: No matter whether the scene is bright or dark, it can ensure that the photographer can get images with equal brightness according to its instructions.

The result is gray or medium gray with a reflectivity of 18%. Designers consider that the colors of most objects in the world belong to medium brightness, which can be used as a standard to adapt to most occasions. Only in this way can we ensure a visible image in most cases. So in a few cases, when the subject is pure black or pure white, it can't adapt and can't be restored. At this time, the photographer has to make adjustments to compensate. For example, if you shoot a large piece of white snow, you have to increase the exposure of 1-2, otherwise gray snow will appear in the photo. For another example, if you take a black camera, you have to reduce the exposure of 1-2, otherwise you will get a gray camera in the photo. If you don't understand this principle and the limitations of the exposure meter, you will screw things up in special occasions, which is especially important when using color reversal films. But the exposure adjustment range of color reversal film is smaller than that of negative film.

When using a hand-held exposure meter, you must pay attention to its light receiving angle. Different exposure meters have different light receiving angles. Generally, the acceptance angle of an exposure meter is similar to that of a standard lens, ranging from 30 degrees to 50 degrees. Some reflected light exposure meters also have the problem of effective distance measurement. Some can measure the light near the object, while others are limited to a few centimeters away.

When measuring distant scenes, if the receiving angle is too large to get readings, then the method of measuring substitutes with similar brightness can be adopted. You can also use the incident light exposure meter to get readings, and judge by experience, you can achieve correct exposure. Of course, the most convenient thing is to use a spot metering meter.

Point photometer

Spot measuring instrument is also a kind of reflected light exposure meter. Generally speaking, a spot light meter refers to an exposure meter with a measuring angle of 1 to 3 degrees. Spot photometers generally have a single function and no facilities for measuring incident light. However, some incident light exposure meters can greatly reduce the acceptance angle after adding accessories, such as measuring 5 degrees.

The advantage of spot light meter is that it can measure the brightness of very small objects. In landscape photography, it can be used to measure the brightness of a scene in a calm place. 1 degree angle photometer can measure the transit of the moon. It can be used to measure the brightness of small parts in product photography. If optical fiber or miniature lamps are used for light distribution in advertisements and product photography, only point meters can be used for light measurement. Therefore, it is a common tool for photographers with strict exposure requirements and photographers who shoot color reversal films.

It stands to reason that when judging exposure with a point photometer, the average brightness should be obtained. For example, the readings measured from the main bright part are1125 seconds, F 16, and the main dark part is1125 seconds, F4. At this time, it is appropriate to press F8 for exposure. You can even measure a few more points and then average the obtained values. In this way, when using black-and-white negatives (the adaptive brightness difference does not exceed one level) and color negative (the adaptive brightness difference does not exceed five levels), the level of detail can be basically maintained. If the light conditions are complicated, the exposure requirements are strict or color reversal films are used, this method is not accurate enough, and a more direct method must be adopted. First find out the most important part that must be reproduced, first consider the exposure according to the brightness of this part, and then consider the care of the secondary part.

If photographers know the "Zone system" advocated by ansel adams, they can use spotlight exposure meter more effectively and accurately. "Partition method" is a method to obtain high-quality images by considering the brightness of the scene and the width of film and photographic paper. Adams divided the scene brightness in black-and-white photography into 1 1 regions, which were expressed in Roman numerals. The O area is the darkest, and the X area is equivalent to the paper base and the brightest. The V region is a middle gray tone region, and the other two key regions are the III region where the shadow part can show details and the VII region where the light part can show details. From zone II to zone VIII, it is a gray spectrum that can record details, which is equivalent to 7 apertures. There is a difference in exposure between adjacent areas. When determining the exposure of a scene, the photographer can first determine an area and prepare to reproduce its shadow level, and then consider the tolerance of photosensitive materials to calculate which other areas can be considered. For example, a shadow part is the most important, so after measuring its reading, reduce the two-step exposure and deal with it in zone III. Then measure the bright part that needs to keep the details. If the reading is 5 levels higher than the shaded part mentioned above, it is exactly zone VIII. In the final photo, it will be bright, but there are still details. If this result is expected, so be it. At this time, if you want to get more and better shadows in the bright part, you have to reduce the development time to reduce the contrast and reduce the brightness of the VIII area to the VII area. On the other hand, if the reading of the main bright part is only three levels higher than that of the main shadow part (area III), it is necessary to enhance the development and improve the contrast. This deductive method is very good for training eyesight. Because in actual shooting, it is often impossible to ensure the true reproduction of the most important part of North Korea by using a point meter, especially when shooting with a color reversal film. Experienced photographers believe that the darker part can be selected as the photometric basis when taking pictures with color negative film, and the brighter part can be selected as the photometric basis when taking pictures with color reverse film. Because the exposure latitude of color reversal film is limited, North Korea will lose its shadow and color due to overexposure, so it is wise to consider ensuring the reproduction of brighter parts first, so that the color of the result will be saturated and dignified, and it will be easy to sell when it is shown on a strong light slide projector. For printing plates, it can remedy the problem of high dye density, but for the commercial film industry sold, it is best to have moderate density and bright colors. On the other hand, photographers in China seem to like slides with dignified colors, so they tend to expose them according to the brighter parts. Photographers in Europe and America follow the principle of standard and moderate density and attach importance to the scientific and technological value of faithful reproduction, so the average photometry method is often used for scenes with uniform light. No matter what kind of thinking, when taking pictures with color reversal film, the exposure range of important parts should be controlled within 1.5 to reproduce the shadow of detail.

When taking pictures with color reversal film, some people advocate that the film sensitivity should be improved first (for example, 1/3), and then the problem of photometric exposure should be considered. This is similar to the exposure principle based on bright parts, but it may not be appropriate in general. Because the actual sensitivity of some color reversal films, such as Fuji Virvia, is lower than the calibration, increasing the usage will inevitably lead to more underexposure and dim images. On the bright side, the elevation sensitivity of these films may have taken into account the adjustment amount, and users can obtain saturated colors through the automatic exposure of the camera. Therefore, when mixing Fuji color reversal film and Kodak color reversal film recently, we should pay attention to the possible sensitivity problems.

How to use the spotlight? You must practice to get familiar with the performance of exposure meter and the characteristics of different films. Finally, there is another trick, that is, closed multi-level exposure, taking one picture according to the measured reading, increasing half-scale shooting and reducing half-scale shooting ... This is a method that experienced professional photographers are unwilling to give up. Films with different densities sometimes have different effects and uses.

Incident exposure meter

The incident light exposure meter measures the light reflected by different subjects, not the light projected by the light source on the subjects. The advantage of this method of measuring illuminance is that it is not affected by abnormal light and shade changes of the subject. As long as the exposure meter is placed on the position of the subject, the translucent spherical receiver is aimed at the camera lens, and the reading is measured, the correct exposure can usually be obtained. In an emergency, exposure can be made according to the reading of incident light without much thinking, and the results are always close. When shooting color reversal films, the incident light exposure meter is very suitable, and the results of measuring illuminance and brightness of the strong light part of the subject are always very close. Therefore, people who shoot color reversal films sometimes like to use the reflected light exposure meter to measure light and then use the incident light exposure meter to check.

The exposure meter of incident light is also limited, so it is impossible for a photographer to get close to the subject every time to measure the light projected on it more accurately. Sometimes photographers have to face several subjects, such as some in the sun and some in the shadow, and they can't cope with them one by one. Therefore, it is also necessary to make a final judgment based on experience.

Use of grey board

When the light is too dim to measure the reading of the subject with the reflected light exposure meter, the gray board can be used instead; This method is most effective when the subject is light and dark and the average reflectivity is equivalent to medium gray. The gray boards sold in photographic equipment stores are paper reflectors with medium gray tone reflectivity 18%. Its back is white and its reflectivity is 90%.

In the case of very dim light, when the reading cannot be measured from the gray surface of the gray board, the white surface can be measured. After measuring the reading, increase the exposure by 2.5 steps. Because the difference between the reflection values of the gray surface and the white surface of the gray board is 2.5.

Some professional photographers always like to carry a gray board with them. When they have doubts about photometry, they can use it as a benchmark to test, so that they can know fairly well.

Since the invention of the exposure meter in the 1930s, the photosensitive materials have been changed for several generations, and the problems of sensitivity and annoying "memory" interference have been solved. But it can't live without batteries. You must use high-quality batteries and carry spare batteries. If the battery suddenly runs out and cannot measure light, you can call "F 16 Irregular Law" for emergency. Set the camera aperture to F 16, and the shutter time is the reciprocal of the film sensitivity (when the film is ISO 125, the shutter time is1125 seconds), which can be handled roughly.

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