This flash terminology guide will give a brief overview of the various terms and idea used commonly with respect to the 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
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)
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
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 shoe mount is a slide in socket rectangular in shape located on the top mirror/prism housing. This socket is used for affixing the external flash unit to the camera. They are also called "Hot Shoe Mount" as they have an electrical trigger which activates the flash unit. The Canon EOS cameras have additional four electrical contacts within the shoe mount which carries signal data apart from the main flash 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 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.
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
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)
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
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 shoe mount is a slide in socket rectangular in shape located on the top mirror/prism housing. This socket is used for affixing the external flash unit to the camera. They are also called "Hot Shoe Mount" as they have an electrical trigger which activates the flash unit. The Canon EOS cameras have additional four electrical contacts within the shoe mount which carries signal data apart from the main flash 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 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.
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
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