This general guide will help to explain to you some of the concepts and terms used in relation to Canon EOS flash photography.
Strobe and Flash.
The words flash and strobe has been used interchangeably actually to denote the same thing. It all depends on whether you are saying it the British or American way. The American refers strobe as a flash unit whereas the British uses the term to refer to anything which produces blinking lights. Speedlight and Speedlite are also two commonly used terms which create some confusion among those new in the photographic world. Speedlite is actually the brand name for Canon series of flash units while Speedlight is the brand name of Nikon series of flashes.
Guide Number
The guide number is the maximum range of a flash unit when it gives out its flash pulse at its maximum setting. However, if you are using automatic flash metering, the number is not relevant. This number only becomes important when you are involved in manual flash settings.
EV (Exposure Value)
Exposure Value or EV is the rating used for determining the sensitivity of the Auto Focus (AF) system or exposure metering for a lens or film type. This number is just a combination of aperture and shutter speed. For example, f2 and 1/125 = EV 9 which is also equal to f4 and 1/30.
Non Dedicated and Dedicated Flash Units
Most Camera manufacturers also manufacture their own line of flash units to complement their camera models. These "own" brand of flash units are known as dedicated flash units. The Canon line of flash units is known as the Speedlite series. They are able to work together with the camera proprietary system to give more precision photography. Non dedicated Flash units are those flash units which are manufactured by third party manufacturers. Usually generic in nature, they cannot communicate with the camera proprietary system.
Shoe Mount
The rectangular slide-in socket which is usually located on top of the mirror or prism housing is known as the shoe mount. This mount is usually used for affixing the external flash unit to the camera. Sometimes it is called a Hot Shoe Mount as it has an electrical trigger to initiate the flash unit once the external flash is fixed to the camera. The Canon EOS Cameras have 4 additional contact points in the shoe mount which helps to transmit flash data from the trigger.
Redeye Effect
When the light from a flash unit is reflected back into the camera off the walls of the retina, this will produce the Redeye effect which we always see in pictures taken in low ambient light conditions. This due to the fact that the low ambient light condition causes the pupils of the eyes to dilate bigger and the color red is because the retina walls are lined with red blood vessels.
Redeye Reduction
To overcome the problems of Redeye effects, you can increase the distance between the flash and the lens of the camera. Or you can also reflect the flash light off the walls instead of direct illumination on the subject. An alternative way is to get the subject to look at a bright light just before taking their picture. What this does is to cause the pupils of the eyes to dilate smaller resulting in less reflection from the retina. - 16738
Strobe and Flash.
The words flash and strobe has been used interchangeably actually to denote the same thing. It all depends on whether you are saying it the British or American way. The American refers strobe as a flash unit whereas the British uses the term to refer to anything which produces blinking lights. Speedlight and Speedlite are also two commonly used terms which create some confusion among those new in the photographic world. Speedlite is actually the brand name for Canon series of flash units while Speedlight is the brand name of Nikon series of flashes.
Guide Number
The guide number is the maximum range of a flash unit when it gives out its flash pulse at its maximum setting. However, if you are using automatic flash metering, the number is not relevant. This number only becomes important when you are involved in manual flash settings.
EV (Exposure Value)
Exposure Value or EV is the rating used for determining the sensitivity of the Auto Focus (AF) system or exposure metering for a lens or film type. This number is just a combination of aperture and shutter speed. For example, f2 and 1/125 = EV 9 which is also equal to f4 and 1/30.
Non Dedicated and Dedicated Flash Units
Most Camera manufacturers also manufacture their own line of flash units to complement their camera models. These "own" brand of flash units are known as dedicated flash units. The Canon line of flash units is known as the Speedlite series. They are able to work together with the camera proprietary system to give more precision photography. Non dedicated Flash units are those flash units which are manufactured by third party manufacturers. Usually generic in nature, they cannot communicate with the camera proprietary system.
Shoe Mount
The rectangular slide-in socket which is usually located on top of the mirror or prism housing is known as the shoe mount. This mount is usually used for affixing the external flash unit to the camera. Sometimes it is called a Hot Shoe Mount as it has an electrical trigger to initiate the flash unit once the external flash is fixed to the camera. The Canon EOS Cameras have 4 additional contact points in the shoe mount which helps to transmit flash data from the trigger.
Redeye Effect
When the light from a flash unit is reflected back into the camera off the walls of the retina, this will produce the Redeye effect which we always see in pictures taken in low ambient light conditions. This due to the fact that the low ambient light condition causes the pupils of the eyes to dilate bigger and the color red is because the retina walls are lined with red blood vessels.
Redeye Reduction
To overcome the problems of Redeye effects, you can increase the distance between the flash and the lens of the camera. Or you can also reflect the flash light off the walls instead of direct illumination on the subject. An alternative way is to get the subject to look at a bright light just before taking their picture. What this does is to cause the pupils of the eyes to dilate smaller resulting in less reflection from the retina. - 16738
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
