How to use camera flash

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1. Understanding the flash number

The flash number (GN) is one of the standards for measuring flash power. It has two functions: one is for manufacturers to identify the power of the flash. The larger the value of GN, the greater the power. Second, when using manual flash photography, calculate the aperture size of the flash exposure. The formula is GN value = aperture × distance (based on ISO100). For example: when the flash GN value = 20 (calculated in meters), when the distance from the subject is 5 meters, the aperture is set to F4 and the exposure is normal. When the subject distance is changed to 10 meters, the aperture needs to be set to F2 for effective exposure.

When the flash power is not enough, you can use the method of increasing the aperture and ISO. Increasing the aperture can increase the amount of light entering, but at the same time the depth of field will be affected, so generally to obtain more power, the method of increasing the ISO is used.

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2. The function of the shutter

The characteristics of flash are fast and strong. Light strikes instantly in the form of strong light, usually completing the flash within 1/1000 second to 1/10000 second. This extremely short exposure time can enter the photosensitive element through the lens much faster than the shutter speed, so generally speaking , when the aperture and output power remain unchanged, the shutter speed does not affect the flash exposure, but it will affect the ambient light exposure. For example, when you use 1/15 second and 1/500 second to shoot the same scene respectively, the flash has completed the exposure at the same speed of 1/1000 second, so the exposure of the flash subject will not change, but the scene will change. Exposure, 1/15 second will be much brighter than 1/500 second.

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3. Flash mode

Manual mode is also used by experienced photographers. It uses the formula of GN value = aperture × distance to make relevant calculations. Adjustment. The amount of light output at this time is set by the photographer based on the actual situation, which can achieve the ideal flash effect. For example, after adjusting the amount of light input, use exposure lock, and then adjust the shutter speed to show the ambient light. But the disadvantage is that each adjustment takes time, which is not conducive to capturing photos.

Auto mode, in this mode, after we fix the flash and lens aperture size (need to be consistent), within the effective range of the flash power, the flash will calculate according to its own photosensitive system Whether the fill light is sufficient or not, the size of the flash output is automatically controlled to achieve accurate exposure. At this time, you can adjust the exposure through the aperture.

TTL mode is also an automatic mode. TTL is the abbreviation of "Through the Lens", which means "through the lens". The method is that light enters the body's metering device through the lens, and the output of the flash is measured, which is more accurate. Canon has E-TTL and Nikon has i-TTL, which all mean the same thing. When the shutter is triggered, the flash also triggers fill light, and the reflected light is used to calculate whether the amount of fill light is sufficient. If underexposure is detected, the flash output will be automatically increased to achieve sufficient exposure.

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4. Flash exposure compensation

The automatic flash mode only gives a normal exposure, and many times we need to increase or decrease the exposure. Meet shooting needs. This is similar to the method of adjusting the camera's exposure compensation. The exposure compensation on the flash can adjust the light output to achieve the desired effect.

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5. Flash bracketing

Flash bracketing (FEB) works on the same principle as the camera's automatic bracketing (AEB). In this mode, the user can select a specific range of exposure (1/3, 1/2 or 1Ev). Usually, 3 shots will be taken in one shot (0Ev, +Ev, -Ev). The bracketing exposure can make the shooting results better. More reliable.