Sep 16 2007
Flash
You’re probably wondering how I can write an entire post just on flash. Well, there’s actually more to flash photography that many people realise.
Flash is generally over-used, and can ruin a photo more often than it saves the image.
On compact digital cameras, there is often no choice as to when the flash can be used, but if you do have this functionality, I encourage you to use it.
The distance your flash will work at, is dependant on the Guide Number (GN) of your in-camera or external flash. In the user manual you should find a GN table, listing the distances your flash will work to.
As you would expect, the flash will be strongest closer to you, and narrow the span, like a tunnel, the further away it’s expected to work. This creates shadows and uneven light in an image, which isn’t generally a desirable outcome.
Flash is a very cold form of light, and can often wash out colours, including skin tones. Where there is a contrast in lighting, if the flash isn’t used correctly it can result in a washed out background, or a very dark foreground.
Using fill flash can help solve this problem.
Fill Flash
Say you want to photograph a person with a view in the background. The problem is the person is in the shade and the background is in full sun.
How can both be correctly exposed? By using fill flash!
Fill flash is exactly that – it fills the frame with extra light, so you can gain a correct exposure in the immediate foreground.
Here is a breakdown for SLR users:
Ø Set your camera to M
Ø Choose an Aperture (if in doubt, use f8.0)
Ø Focus first on the background by half pressing the shutter
Ø Based on the exposure reading, now set the shutter speed, so that the exposure indicator is in the middle of the bar
Ø Make sure the shutter speed doesn’t exceed the Flash Sync Speed (see below)
Ø Turn the flash on
Ø Focus now on the person’s face (particularly the eyes), and realign to take into account the Rule of Thirds
Ø Take the photo!
What you should now have is a photo with a correctly exposed background, and a nice clear picture of the person’s face.
Fill flash can be used in a number of situations, but I’ve found this to be the most common.
Flash Synchronisation Speed
Every camera has a flash sync speed and it varies from camera to camera. The sync speed means you will only be able to use the flash up to a particular shutter speed (e.g. my camera will only allow me to use the flash for shutter speeds of 1/250 sec and slower).
The rationale behind imposing a limit is that if you can take the photo at a faster shutter speed, there should be enough light without using the flash.
If you take a photo using flash with a shutter speed higher than the flash sync speed, the shutter will have opened and closed before the flash fires, resulting in an underexposed photo.Or the shutter could be half way through its cycle when the flash goes off, so that half of the picture is dark and the other half is lit by the flash.
When using the camera in its manual and semi-manual modes, you need to be mindful of this level – you’ll find it in your instruction manual.
If the exposure is asking for a faster Shutter Speed than the flash sync speed (1/250 in my case), then set the Shutter Speed to the highest level you can, and adjust the Aperture until the frame is correctly exposed.
Remember, flash has its advantages, but first try taking the photo without it, then if necessary, use fill flash.
