The Canon Camera Flash Terminology Guide
This general guide will help to explain to you some of the concepts and terms used in relation to Canon EOS flash photography.
Flash units 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
The maximum distance which a flash unit can reach with its flash pulse is known as the guide number. But if you are using automatic flash metering, this number is not important at all. You will only need to know this number when you are more inclined to do manual settings for your flash.
Exposure Value (EV)
EV or Exposure value is the value used for deciding the sensitivity of the AF (Auto Focus) system or exposure metering which respect to film types or lenses. You need to combine the aperture and shutter speed together to get this value. For example, 1/125 and F2 is equal to EV9 which is also equivalent to F4 and 1/30.
Dedicated or Non dedicated flash units
Camera Manufacturers like Canon manufacture their own line of flash units to cater for their own range of cameras. The Canon line of flash units is known as the Speedlite series. These flash units are able to communicate with camera system thus allowing the photographers to enjoy more precision photography. They are called dedicated flash units. Non dedicated flash units are those flash units which are manufactured by third party manufacturers. They are usually generic and are not able to communicate with the camera 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.
The 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.
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