This is a great technique to master, particularly if you shoot weddings or environmental portraiture. Imagine the scene - 100+ wedding guests to photograph - typical UK summer weather - pouring with rain! Should you stick on your “oncamera” flash and shoot on programme so that your shots look just like those taken by all the guests? Or, do you take the opportunity to set up a light or two and produce some rather special pictures?
Of course the latter is a much better alternative, but then there is the problem of balancing your flash with the daylight. Since you won’t want the view through any windows or doors in the photograph to look like night time, let’s do the balancing act!
|Inside and outside balanced 1/125 @ f8.
Choose a flash synchronisation shutter speed and set that on your camera - let’s say 1/125th.
Point your camera through the window and see what aperture you would need to use at 1/125th to get a correct exposure (or, you can also use a hand held meter). Let’s say for example its f8, this means if you were to set your camera to 1/125th at f8 and take a picture through the window it would be correctly exposed.
Set-up your light(s) inside and using a flash meter, adjust them to give you f8 inside as well. (Note - make sure the lights are not reflected in the windows!)
With your camera set to 1/125th and f8 the photo will be correctly exposed both inside and out. But to make the outside appear a little brighter than inside and therefore look more natural simply reduce your shutter speed. If you were to drop your shutter speed to 1/60th the outside would be 1 f-stop over exposed - 1/30th and it would be 2f-stops over etc.. But, the inside will remain correctly exposed as this is being illuminated by the flash and the longer exposure does not vary this. In fact, it is the flash duration that freezes the image - you can even hand hold at ridiculously slow speeds so long as you are using a flash with a fast flash duration and the ambient light levels
inside the room are not too high.
Note: For this reason it is always beneficial to select flash units that combine good fast flash durations with excellent low power stability - many do not. These are just a couple of advantages of the latest professional digital units.
|Shutter reduced to 1/60th @ f8.