This guide will seek to provide you with an explanation of the various concepts and terms which are used which respect to Canon EOS flash photography.
Flash units and Strobe
What is the main difference between a Flash and strobe is just whether you are using UK or US English. We refer a strobe as a flash unit in the US whereas the British uses the word as meaning anything which emit blinking lights. Other commonly used terms which cause confusion in flash photography are the words "Speedlight" and "Speedlite". Speedlight is actually the brand name of Nikon series of flash units while Speedlite is the brand name of Canon series of flash units.
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)
Used for determining the sensitivity of the Auto Focus or (AF) system or exposure metering for film types or a lens, the EV or Exposure Value is a combination of both Aperture settings and Shutter speed. The numbers 1/125 and F2 give an EV value of 9 which can also be obtained from F4 and 1/30.
Dedicated or 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.
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 circumvent around the problem of redeye effect, there are several ways to go about this. One effective way is to move the flash away from the lens or reflect the flash light off the walls onto the subject instead of directly illuminating the subject. Another way is to get the subject to view a bright light just before taking the picture of the subject. This causes the pupils of the eyes to dilate smaller and therefore decreasing the reflective effect of the retina. - 16069
Flash units and Strobe
What is the main difference between a Flash and strobe is just whether you are using UK or US English. We refer a strobe as a flash unit in the US whereas the British uses the word as meaning anything which emit blinking lights. Other commonly used terms which cause confusion in flash photography are the words "Speedlight" and "Speedlite". Speedlight is actually the brand name of Nikon series of flash units while Speedlite is the brand name of Canon series of flash units.
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)
Used for determining the sensitivity of the Auto Focus or (AF) system or exposure metering for film types or a lens, the EV or Exposure Value is a combination of both Aperture settings and Shutter speed. The numbers 1/125 and F2 give an EV value of 9 which can also be obtained from F4 and 1/30.
Dedicated or 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.
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 circumvent around the problem of redeye effect, there are several ways to go about this. One effective way is to move the flash away from the lens or reflect the flash light off the walls onto the subject instead of directly illuminating the subject. Another way is to get the subject to view a bright light just before taking the picture of the subject. This causes the pupils of the eyes to dilate smaller and therefore decreasing the reflective effect of the retina. - 16069
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
