What is the meaning of flash index and the relationship between power distance (its use tutorial)

I posted a flash operation skill yesterday, but a friend said that I didn't understand it. So this morning, I edited and arranged a bunch of introductory tutorials on flash, and tried to speak in vernacular. I hope my friends can understand this time.

Photography and Light —— Use Skills of Flash

Photography is closely related to light. Without light, the world will be dark and photography will cease to exist. All kinds of light existing in nature have an indispensable key influence on the tone, atmosphere and level of objects and photographic images. When the photographic light is insufficient, artificial light will be used to make up for the light. The hot shoe flash that comes with the camera is the most commonly used light source in shooting. Because it is convenient to carry, the color temperature of light is very close to natural light. It is the most widely used artificial light source. Here are some basic knowledge about the use of flash, so that you can have a clear understanding of flash and better apply it to photography.

Vernacular flash tutorial, 8 strokes to get started with flash basic operation.

1. What is the flash index?

We often say that the flash index refers to the standard value of flash working power, which is expressed by GN. There are two main uses:

It is the basis for manufacturers to identify flash power. The value of GN is proportional to the power, and the greater the value of GN, the greater the power.

Calculate the aperture of flash exposure, which will be used when manually adjusting flash shooting. The relation principle is GN value = aperture distance.

Take the flashing light GN value =20 as an example. When the object distance becomes10m, the aperture is set to F2 effective exposure, while when the object distance is 5m, the aperture needs to be set to F4 normal exposure.

Vernacular flash tutorial, 8 strokes to get started with flash basic operation.

So when the flash power is insufficient, it can be balanced by increasing the aperture and ISO value. Generally, the method of increasing ISO is adopted to obtain higher power. Because increasing the amount of light entering by increasing the aperture will affect the depth of the scene.

Second, the relationship between flash and shutter

Flash is instantly emitted in the form of strong light, which is characterized by rapidity and intensity. Blinking is usually completed within11000 seconds to110000 seconds. The light enters the photosensitive element through the lens at a speed faster than the shutter speed, and the exposure is completed in a very short time. Shutter speed will not affect the exposure of the flash, but it will. Environmental exposure is inversely proportional to shutter speed. When shooting the same scene only by changing the shutter speed, using the shutters of115 seconds and 1/500 seconds respectively, the flash will finish the exposure at the same speed in advance, so the same exposure of the flash body will affect the exposure of the scene, and115 seconds will be more than/kloc-.

Third, the common modes of flash

There are generally three flash modes: manual mode, TTL mode and automatic mode.

Manual mode refers to manual adjustment, which is based on the relationship principle of GN value = aperture distance. This mode is mostly used by experienced photographers. Manual adjustment can set the relevant value according to the actual situation. After adjusting the transmittance, use the exposure lock, and then adjust the shutter speed to make the ambient brightness brighter or darker. It can achieve the ideal flash effect that photographers want. But every adjustment takes time, which is not conducive to capturing and missing wonderful moments.

In TTL mode, TTL means "through the lens", which means "through the lens". This is an intelligent automatic mode. The principle is that light enters the light metering device of the fuselage through the lens to measure the output required by the flash. When the shutter is triggered, the flash also triggers the fill light: whether the fill light exposure is sufficient is calculated by the reflective flash, if the exposure is sufficient; If underexposure is detected, the flash output will automatically increase. More accurate. Canon has E-TTL, Nikon has i-TTL, and the principle mode is similar.

In automatic mode, the flash calculates whether the light is sufficient according to the following information.

4. What is flash exposure compensation?

Auto flash mode is only the normal exposure measured by the machine. In many cases, the measured exposure may not meet our photographic needs. At this time, it is necessary to increase or decrease the exposure to meet the needs of photography. This is flash exposure compensation, similar to the exposure compensation method of camera. The exposure compensation on the flash can achieve the desired effect by adjusting the transmittance.

Verb (abbreviation for verb) What is flash exposure?

Flash surround exposure is a kind of exposure circle, which works like a camera. In this mode, users can select a specific exposure range and take 3 photos. Usually, this is the way to take pictures. The use of enclosed exposure can make the light receiving surface of the object more comprehensive and the shooting effect more reliable.

6. What is flash zoom?

The flash and zoom are synchronized with the zoom of the lens, which is consistent with the field of view under the same focal length of the lens. Similar to the principle of lens zoom, flash zoom is also to cover more exposure range. In TTL mode, the flash will automatically adjust to match the focal length of the nearest lens. Changing the focal length of the flash will change the projection distance and intensity of the light beam. When the focal length is larger, the light beam will gather and cover a smaller area, and the light intensity will be stronger.

With a small focal length, the light of the flash can cover a wider range and the light becomes much softer.

7. What is used for high speed?

High-speed synchronous flash is a mode when capturing moving objects. It can be cured quickly, and it is very suitable for large aperture to control the depth of field and make the background as clear as well. You can get rid of the limitation of flash synchronization and reach a higher shutter speed, or 1/8000. However, this mode has a disadvantage, and it usually needs to be shot close to the subject because the intensity of the flash is not strong enough.

Eight, what is slow synchronization?

Slow synchronization means slowing down the shutter speed and brightening the ambient light. As mentioned above, this is an operation skill mode based on the principle that the longer the shutter time, the brighter the ambient light. Slow synchronization can use the superposition of ambient light and flash: the shutter speed determines the background brightness, and the flash determines the subject brightness. The camera can synchronize the flash with the shutter. At this highest synchronization speed, the exposure of the subject and background will eventually be consistent, which is usually synchronized with Hou Lian. Used for portrait photography at night to achieve the effect of synchronous light reception of the whole picture.

If you don't understand this, then Bian Xiao is included. I feel that this is already very vernacular. If it really doesn't work, try more and you will have experience.

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