Shooting skills of flash photography

The flash from the flash can only last for a short moment, generally less than11000 seconds. To expose the whole film in a short time of 1 millisecond (11000 seconds) means to completely open the shutter covering the whole film at once.

When the slit formed by the shutter curtain passes through the whole film, the exposure is completed. During the short exposure of 1/250, 1/500 or11000 seconds, the focal plane shutter can only open one slit, and then the curtain moves gradually at a slow speed until the whole film is exposed. Obviously, the exposure of strongpoint must be carried out at such a slow speed, so as to ensure that the shutter curtain is completely opened at the moment when strongpoint is issued, thus exposing the whole film.

How slow? The answer is in the user manual of the camera, and the corresponding camera synchronization speed will be clearly told in strongpoint. Traditionally, the synchronization speed is about 1/60 seconds. That is to say, it takes 1/60 seconds for the shutter to fully open. When shooting with strongpoint, if the shutter speed is slower than 1/60s, it is impossible to expose the whole film. Because when the strobe reaches the maximum light intensity, a part of the film is covered by the shutter that is not fully opened within 1 millisecond, so this part of the film is still black.

What is the synchronization speed of the camera? Again, these can be found in the manual of the camera. Synchronization speed refers to the shutter speed normally set on the camera when shooting with strongpoint. The most unexpected thing is that many special flash devices can automatically set the camera to the correct synchronization speed, regardless of the shutter speed set by the camera. This is also an advantage of using a dedicated flash. Remind everyone, don't forget to set the shutter speed to synchronous speed.

There are two ways to connect the flash device and the synchronization device of the camera. One way is to plug the flash into the socket of the camera. Strongpoint and the camera communicate with the synchronization device through the corner in the hot shoe socket. Another method is to connect strongpoint to the camera with a pc cable (pc stands for press contact). One end of the pc cable is plugged into the socket of the stroboscope, and the other end is plugged into the electronic flash socket of the camera. Please note that the old camera has two flash sockets. One of them is an electronic flash socket, which is usually marked with an X symbol or a lightning symbol. The other socket is used for the flash bulb, which is marked ep (focal plane shutter camera) or M (mirror shutter camera). Therefore, when using strongpoint, especially when using pc cable connection, it must be plugged into the correct socket.

When using strongpoint, the manual of the camera will display the synchronization speed, for example, 1/60 seconds. This is not to say that only this speed can be used for flash shooting, but the highest shutter speed when shooting. You can choose any speed lower than this speed in actual shooting. That is to say, if the user manual indicates that the synchronization speed of strongpoint is 1/60s, then shooting at 1/30s or1/5s or even slower is synchronization, because the shutter will be fully opened at these slower speeds.

However, why don't people deliberately choose synchronous exposure below the prescribed speed when taking pictures? Because if we do this, we may risk getting double images on one picture, one is generated by strongpoint flash, and the other is generated by other lights in the scene. The slower the shutter speed is set, the more likely it is to shoot a ghost. Sometimes, even if we set the shutter speed to1/60s, if other lights in the scene (except the flash) are strong, it is still possible to shoot ghosts. For example, when shooting a boxing match at the guardrail, you may encounter such a problem: because the stadium lights are too bright, the boxer's fast-swinging fist seems to be divided into two parts in the photo-one part is a clear image produced by instantaneous flash, and the other part is a blurred image produced by the exposure of the stadium lights within full shutter 1/60 seconds.

In the past,1/60s was the fastest synchronization time for most focal plane shutter cameras. This is because most of these shutters are made of cloth and can only move slowly. Now new space materials are adopted, and faster synchronization speed is obtained. For example, some single-lens reflex cameras are characterized by a titanium shutter with a synchronization speed of 1/250 seconds. Exposure at such a fast speed has actually solved the problem of photo ghosting.

The last thing to note is. So far, all we have discussed are cameras with focal plane shutters. How to choose the synchronization speed for a camera with a mirror shutter? Fortunately, for any short exposure time, the inter-mirror shutter can be fully opened during the exposure time. In other words, we can perform flash exposure at any shutter speed, no matter how fast, 1/25, 1/250 or even11000 seconds. Faced with such a fast speed, we don't have to worry about taking ghost photos at all. This is a prominent advantage of mirror shutter.

The commonly used flash synchronization methods are M, X and FP or F..m synchronization, which is suitable for most flash bubbles and leaf shutters, and the shutter speed can be as high as 1/500 seconds. X-type is set to synchronize the electronic flash with the blade or focal plane shutter. When using focal plane shutter and flash bulb, you need to use FP or F synchronization mode. When X-type synchronous blade shutter is used, the electronic flash can be synchronized with any shutter speed. Flash bubble takes 1/30 seconds.

Flash exposure is usually calculated by flash index. The flash index of electronic flash lamp depends on its luminous quantity, and the unit of luminous quantity is beam candle seconds (BCPS) or effective candle seconds (ECPS). The aperture value required for correct exposure can be obtained by the flash index and the following formula:

Flash index The distance from the flash to the subject (unit. Feet) = aperture value

For example, the flash index is 64, and the distance between the flash and the subject is 8 feet:

64/8=8 Aperture should be set to f/8.

Please note that the flash index in the above formula is calculated in feet. If it is changed to meters, it needs to be calculated by dividing the flash index by 3.28. Some electronic flashlights automatically control the flash. When using this flash, as long as an aperture is selected according to the sensitivity of the film within a certain distance, the flash will automatically control the flash duration to obtain the correct exposure without using the above formula for calculation.

Use of Flash/strongpoint.

There are three basic ways to use flash or strongpoint.

Mounted on a camera

The easiest way is to install a flash on the camera. Large portable equipment can be fixed on the bracket, screwed into the tripod screw hole at the bottom of the camera, and then connected to the synchronization mechanism of the camera through a synchronization line (also called pc line). Small equipment can be directly plugged into the accessory socket of the camera, some cameras are connected by wires, and some cameras are automatically connected with flash equipment and synchronization equipment through hot shoe sockets without additional wires.

Stay away from the camera and connect with wires.

In order to get more flexible lighting, we can keep the flash or flash away from the camera and connect the synchronization device with an extension cord. This connection technology is widely used, from the small flash in the hands of wedding photographers to the bulky strobe device used in the complex light source combination in the studio. Wedding photographers can shoot with a flashlight in their left hand and a camera in their right hand. In the studio, the camera is usually fixed on a tripod, and then a set of wires are led out from a separate flash synchronous control box to connect three or more high-power flash devices with the camera. As we introduced in this lesson, this off-line connection technology enables us to choose different lighting effects more freely than the connection technology of installing flash devices directly on the camera.

The flash on the camera triggered the follower.

Slave is a photosensitive element, which can automatically trigger the flash under the strong light excitation of other flashlights. We can arrange some driven devices in different positions, and lighting the basic flash can trigger these driven devices to flash at the same time. All these flash devices don't need any wire connection. Simple slave units can be bought for a few dollars, and most strobe devices can be plugged in. If you want to add some photographic tools to yourself, the driven unit is very convenient.

When the shutter button is pressed, the strongpoint installed on the camera will flash immediately, and the released flash will trigger the driven unit and make the driven Strongpoint flash.

Compared with electroluminescent lighting, stroboscopic equipment has the following important advantages in the studio: strong light is brighter than the light released by 500-watt overflow lamp, even when using small spots. Therefore, we can get a larger depth of field with a smaller aperture. Short duration up to 1/50000 seconds to capture any action. The bullet in flight has been successfully fixed with a special high-speed strobe device.

Cold light is different from hot light emitted by overflow lamps and spotlights. Strongpoint's light is cold and short-lived, which will not bring the discomfort that the model can't open his eyes. This is especially beneficial when photographing children, animals or heat-sensitive objects such as food or flowers.

But in the studio, stroboscopic equipment also has a big disadvantage. Can you guess? Yeah, I just can't see the lighting effect in advance. For overflow lighting, what you see is what you get, while for strong point lighting, you can only see its lighting effect when you see photos.

However, everything can be remedied. Many studio strobes have the function of modeling lighting: incandescent lamps can be turned on when the lighting is distributed. Its light is much stronger than the flash of stroboscopic device, but the irradiation area and flash area are exactly the same, and the light intensity of modeling is often proportional to the light intensity of strongpoint.

Therefore, with the help of modeling lights, we can arrange all strobe devices like ordinary overflow lights, such as main lights, auxiliary lights and background lights. If the strobe device is not properly arranged, the strong light area and shadow area will appear in the modeling light. Keep moving the styling lights until we see the desired effect, and then we can shoot with strongpoint.

(1) flash index

The flash index is obtained by multiplying the distance of the subject by the aperture coefficient according to the instantaneous luminous intensity of the flash, and is usually represented by the symbol gn. Flash index is an important factor affecting exposure in flash photography. Therefore, when we use flash to take pictures, we must first understand and master the flash index of the flash used.

The international standards for measuring the flash index of flash lamps are basically unified. Many manufacturers of photographic equipment are iso systems published by the International Organization for Standardization, and the measurement standard is the sensitivity of ISO 100/2 1.

If the sensitivity of the film we use is not ISO 100/2 1, how to convert the flash index? Now a flash index conversion table is listed for your reference. As long as a series of conversion factors listed in the table are multiplied by the flash index of ISO 100/2 1, the flash index of any other photosensitive film can be easily converted (the film sensitivity in the table is calibrated in gb system).

Conversion table of flash index of films with different sensitivities

Film sensitivity1518 2124 27 30 33 36

Conversion coefficient (times) 0.50.711.422.845.6

For example, with gb2 1 degree film, the flash index of a flash is 22, and with gb24-degree film, the flash index of the flash is 22×1.4 = 31; When using gb27-degree film, the flash index of the flash is =22×2=44, and so on.

② Application of Flash Index

We already know that the flash index (gn) is equal to the product of the distance between the flash and the subject and the aperture coefficient used by the camera, so it can be expressed by the following formula:

gn=l×f

Where gn stands for flash index; L represents the distance from the flash to the main body; F represents the aperture coefficient used.

The flash index indicates the brightness of the flash. The greater the index, the stronger the brightness; The smaller the index, the weaker the brightness. However, when reading the flash index, we should pay attention to the units marked behind the index, which are usually divided into 2 1 degree/meter and 2 1 degree/foot. In application, the length unit of lighting distance must be consistent with it, which can not be ignored. If the metric index is mistaken for the metric index, the photographic exposure will be seriously insufficient; On the other hand, if the metric index is wrongly used as the metric index, the photographic exposure will be seriously overexposed.

When all kinds of electronic flashlights leave the factory, the manufacturers attach instructions, including the flash index recommended by the manufacturers. The flash index recommended by some manufacturers is often high, so when a photographer uses a new flash for the first time, he should take the flash index recommended by the manufacturer as reference data and determine an accurate flash index through actual shooting tests. The test method is as follows: in the dark environment, aim the flash at the subject and shoot multiple negatives with the same illumination distance and different aperture coefficients; Or shoot multiple negatives with different illumination distances under the same aperture. Record all the above tests, and then develop the negative according to the standard development conditions for observation and analysis. The film with the most normal density is the correct exposure. By applying the formula of flash index, the accurate flash index of the flash lamp can be obtained by multiplying the illumination distance of the film by the aperture used. This is commonly known as the practical flash index.

If the actual flash index is consistent with the flash index recommended by the manufacturer, it proves that the flash index recommended by the manufacturer is reliable. If the actual flash index is lower than the flash index recommended by the manufacturer, it proves that the recommended index is on the high side, and the exposure combination should be determined according to the actual index when shooting.

When we master the practical flash index of starlight lamp, we can calculate the aperture coefficient at any time according to the different distance between the flash lamp and the subject in photography practice. The formula is: aperture = exponential distance.

The flash index of flash is the main basis for determining the exposure combination in flash photography. But in practical application, the flash index can be adjusted according to the specific situation. For example, when the flash lamp is used as supplementary lighting for the shadow part under natural light conditions, it is usually necessary to increase the flash index of the flash lamp by 50% to calculate.

In some cases, in order to obtain the soft light of flash lighting and avoid the obvious projection caused by flash lighting, indirect flash lighting is often used, that is, flash lighting shines on the ceiling or wall, and then faces the subject reversely. To determine the exposure combination of indirect flash, we should first consider the reflectivity of white ceiling or wall at about 70%, then measure the distance from the flash lamp to the ceiling or wall and the distance from the reflector to the subject, and then divide the flash index by the sum of the two distances and multiply it by 70% to get the aperture coefficient required for indirect flash photography.