Canon EOS Flash Photography Explained
One of the most common confusion which occurs with the Canon EOS flash photography is the fact that the Canon EOS modes like the Program (P ), Shutter Priority (TV) , Aperture Priority (AV) and Manual (M) modes handle flash illumination is different ways. This is especially so when the ambient light is not strong. This guide will give a brief run down of how the various modes work when the flash is activated. This guide also assumes that the FP mode is not turned on.
The P (Program) Mode
With the P mode, The Shutter speed is set to the highest possible speed to let you be able to hold the camera with your hands. You will also not have the problem of motion blur since the shutter speed is set fast enough to compensate for the low ambient light conditions. The P mode also functions when the ambient light is high. Under High ambient lighting conditions, the Camera will assume that the foreground will be flashed filled. Therefore, the output of the flash will be low powered. Conversely when the ambient light is low, the flash will be adjusted to give a higher output. The shutter speed will also be adjusted accordingly. But the picture will result in having a dark background.
Shutter Priority (TV) Mode
With this mode, the Camera lets you decide the shutter speed instead. It will decide on the aperture priority settings to suit the shutter speed that you have chosen to make sure that the exposure level is correct. The flash pulse duration will be decided by the flash metering system. In essence the Camera will always function under fill flash mode when in TV mode. This is the opposite of the “P” mode. The Canon EOS system will also indicate to you if the background is too dark. You will see this warning when the Maximum aperture settings begin to blink in the viewfinder. If this happens, you have to reduce the shutter speed and use a tripod stand to hold the camera to avoid motion blurring.
AV (Aperture Priority) Mode
If you are using the Aperture priority mode, you can determine the camera depth of field (DOF) when you adjust the lens aperture. What the camera will do instead is to adjust the shutter speed to expose the background to the right exposure. The duration of the flash pulse will be determined by the camera flash metering system as well. Pay attention that the shutter speed is set low or not. If the shutter speed is set low, you will need to use a tripod to hold the camera. Otherwise, you will end up with pictures which are blurred because of motion. Here in this mode, the camera will also work in fill flash mode just like under TV mode. Canon has several camera models which possesses a function which allows you to synchronize the X-Sync speed to the Shutter speed. The models which have this function are the Canon Elan II/ EOS 50 and the EOS10/10s.
M (Manual ) Mode
Under this mode, you will specify both the shutter and aperture speed of the camera. You will also determine the exposure setting of the camera. The camera will, through the flash metering system, calculate the flash output to illuminate the fore-ground.
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