When Harold Edgerton invented the modern electronic flash in 1931, the world of photography was revolutionized. The principle behind the electronic flash is that when you charged up a capacitor or condenser and release the energy through a flash light bulb (A glass bulb containing inert gases), a split second burst of light will occur. This output of light occurs instantly when you send power to the flash light bulb. Therefore you can control this output of light through regulating the duration of electrical pulses to be sent to the flash light bulb. Before the advert of modern electronics, the duration of electrical pulses used to be controlled by a component called the thvristor. Today, modern electrical circuitry has taken over the function of this component.
Generally, there are two ways to control the quantity of light that enter the camera. The first way is adjusting the speed of the shutter which will affect how long the exposure time will be. The second way is through adjusting the aperture of the lens. This will determine how much light will enter the camera. Although you can use filter to block out additional light but here we will only talk about the fundamental ways of how to control flash exposure. Flash photography is an entirely different ball game because the flash pulse involves only micro seconds' display of light. As such, the mechanical shutter speed does not play any part in determining the amount of light which enter the camera except when the camera is in FP mode.
The speed of the camera's shutter is only important when the ambient light is a continuous source. But the duration of a flash pulse is too brief for the camera mechanical shutter to even react to the change of light. Therefore the way to control the quantity of a flash pulse entering the camera is by:
Change the physical diaphragm of the camera lens which is the lens aperture. Doing so allows you to control the amount of light that can enter the camera.
You can also adjust the physical distance from the flash unit to the subject. This will also control the quantity of light going into the camera. The laws of physics dictates that the further the distance between the light source and an object, the lesser the amount of light hitting the object.
One can also control how much light there is between the flash unit and the subject matter by using diffuser. Although this is a possible way, one also has to consider the inconveniences of carrying all these items around on location.
Lastly, we can affect the duration of the flash burst by adjusting the duration of the electrical pulse to the flash unit therefore controlling the amount of light produced. This is the primary ways today how we control electronic flash.
In essence this is what flash metering is all about. Precise adjustment is not easy and usually takes years of experiences before one can correctly determine the amount or duration of the electrical pulse to set the flash unit too. Fortunately modern Camera like the Canon EOS digital camera has automate the system making it a breeze even for the novice to set the duration of the flash burst to take the ideal picture. - 16463
Generally, there are two ways to control the quantity of light that enter the camera. The first way is adjusting the speed of the shutter which will affect how long the exposure time will be. The second way is through adjusting the aperture of the lens. This will determine how much light will enter the camera. Although you can use filter to block out additional light but here we will only talk about the fundamental ways of how to control flash exposure. Flash photography is an entirely different ball game because the flash pulse involves only micro seconds' display of light. As such, the mechanical shutter speed does not play any part in determining the amount of light which enter the camera except when the camera is in FP mode.
The speed of the camera's shutter is only important when the ambient light is a continuous source. But the duration of a flash pulse is too brief for the camera mechanical shutter to even react to the change of light. Therefore the way to control the quantity of a flash pulse entering the camera is by:
Change the physical diaphragm of the camera lens which is the lens aperture. Doing so allows you to control the amount of light that can enter the camera.
You can also adjust the physical distance from the flash unit to the subject. This will also control the quantity of light going into the camera. The laws of physics dictates that the further the distance between the light source and an object, the lesser the amount of light hitting the object.
One can also control how much light there is between the flash unit and the subject matter by using diffuser. Although this is a possible way, one also has to consider the inconveniences of carrying all these items around on location.
Lastly, we can affect the duration of the flash burst by adjusting the duration of the electrical pulse to the flash unit therefore controlling the amount of light produced. This is the primary ways today how we control electronic flash.
In essence this is what flash metering is all about. Precise adjustment is not easy and usually takes years of experiences before one can correctly determine the amount or duration of the electrical pulse to set the flash unit too. Fortunately modern Camera like the Canon EOS digital camera has automate the system making it a breeze even for the novice to set the duration of the flash burst to take the ideal picture. - 16463
About the Author:
Tim Harris is a canon camera enthusiast. For tips on choosing and buying cameras, do check out Canon OS Camera website. Camera 40D Digital Rebel XTI 3D Blog
