There are times when we review a photograph we have taken on either the rear screen of the camera or on the computer at home, where the resulting image is different to what we had expected. This happens even in what we perceive to be normal lighting conditions so why does it also happen when a flashgun is used?
You know the type of photograph I am talking about? The picture of your group of friends which looks “washed out” as the camera has over exposed the image.
The chances are you set your camera to use flash (either the small pop-up or affixed separately to the camera) in Automatic and are not making allowances for factors in the scene which may affect the exposure. In other words you are letting the camera decide how to expose the image. Cameras are intelligent but are not clever. They do not know the subject you are taking the picture of. Add a flashgun into the equation and you are making their task more difficult.
So what can you do? If you are using the flash as a “fill-in” (additional light source) then the camera is having to work with 2 exposures, one for the ambient light and the second for the flash. It is best you set the camera to Manual and take a light reading of the ambient light.
You will first need to set a shutter speed that is within a range up to the maximum flash synchronisation speed that can be used with your camera (up to about 1/200th).Set the corresponding Aperture value to balance the exposure.
Turn on the flashgun and set the flashgun to automatic.
Look at your subject. Is there a large area of predominately light or dark colours? If there is the chances are your flashgun will be fooled by the dominance of this colour and not expose the shot correctly. A useful thing to remember is that camera meter systems expose for a colour tone that is 18% grey. This means something that is black will be over-exposed so that it renders a grey tone and conversely something that is white will be under exposed so that is rendered grey.
If there are a lot of dark colours, you will need to turn the power of the flashgun down (you can do this my applying “flash compensation”) by 2/3 to 1 stop.
Apply these settings and now take the picture. With modern flashguns they are calibrated to work with your camera’s metering system (TTL – Through The Lens). At the point you half depress the shutter button a small pre-flash may fire. This is the camera attempting to obtain the flash exposure before the shot is taken. When you fully depress the shutter this exposure is remembered and the flash power output applied accordingly. If the resulting image is too dark or too light, you can adjust the flash compensation until you get the result you want.
The picture shown here was taken by firstly taking an ambient light exposure for the background and then setting the flash to light the couple (who were in shade) in the foreground.
To take even more control you can switch your flashgun to manual and then work out the settings manually using flash to subject distance and applying Inverse Square Law.
Want to find out more about lighting? Our Introduction to Flash course covers this in more detail as well as using flashguns off camera and in multiple flash sets.