This general guide will help to explain to you some of the concepts and terms used in relation to Canon EOS flash photography.
Flash and Strobe
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
This number refers to the maximum distance which a flash is range for. This number is irrelevant when you are using the automatic flash metering system. However the number is crucial if you are involved with manual flash settings.
Exposure Value (EV)
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.
Dedicated and Non Dedicated Flash Units
Dedicated flash units are flash units designed by the Camera manufacturers for their own range of cameras. These flash units can communicate with the camera system allowing for more precision photography. For example Canon manufactured the "speedlite" range of flash units for their EOS cameras. Non dedicated flash units are those flash units usually manufactured by third party manufactures. They normally work the same way on all brands of camera with little or no communications with the camera unit itself.
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
A common occurrence with flash photography is the "Red Eye Effect". This happens when the light from the flash unit is reflected back into the camera from it bounces of the red blood vessels of the eyes. The situation tends to occur in environment with low ambient lighting causing the pupils of the eyes to dilate bigger to allow for more light to enter the eyes.
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. - 15437
Flash and Strobe
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
This number refers to the maximum distance which a flash is range for. This number is irrelevant when you are using the automatic flash metering system. However the number is crucial if you are involved with manual flash settings.
Exposure Value (EV)
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.
Dedicated and Non Dedicated Flash Units
Dedicated flash units are flash units designed by the Camera manufacturers for their own range of cameras. These flash units can communicate with the camera system allowing for more precision photography. For example Canon manufactured the "speedlite" range of flash units for their EOS cameras. Non dedicated flash units are those flash units usually manufactured by third party manufactures. They normally work the same way on all brands of camera with little or no communications with the camera unit itself.
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
A common occurrence with flash photography is the "Red Eye Effect". This happens when the light from the flash unit is reflected back into the camera from it bounces of the red blood vessels of the eyes. The situation tends to occur in environment with low ambient lighting causing the pupils of the eyes to dilate bigger to allow for more light to enter the eyes.
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. - 15437
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
