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Flash

March 12, 2010 Leave a comment

Your camera probably comes with a built in flash.  In low light situations when you’re indoors or outside at night you may have to use your camera’s flash to light the scene.  However, don’t rely too much on it because it tends to wash out colors.  In indoor situations it may be best to just up your ISO to above 800 so that you are able to shoot at a fast enough shutter speed to capture motion and get  correctly exposed images.

One good thing to know regarding light is the Inverse Square Law.  The farther that light travels, the more the more the light rays spread out and the dimmer the resulting illumination.

The law states that at twice a given distance, an object receives only one-fourth the light (intensity of illumination is inversely  proportional to the square of the distance from light to subject).  In the image below, only one-fourth of the light falls on an object at 10 ft as from the same light source at 5 feet.

Keep this in mind when using flash as your primary light source, it will not illuminate everything but dicipates rather quickly.  However, in bright daylight you may want to consider using flash for effect.

Check your camera manual for the the distance your flash will reach depending on your f/stop.

Also, check your camera for different Flash modes.

If you have a subject in front of a bright background, you can use Flash Slow Speed Sync (if your camera has that mode) this sets the shutter speed slower while using the flash to capture both the background and the person clearly.

Use Trailing Curtain Sync

Below is an image shot with the Flash in brigth daylight.  Compare that to the image shot without the flash.  Notice how even in bright daylight when there is plenty of sun to give us a rich colorful image, the one with the flash is washed out.  However, notice how the flash has filled in the areas where there would be shadows, this gives us detail in the shadow areas but robs the image of depth.

The Image below was shot with no flash, notice the colors are richer.  However, notice that the shadowed areas dont have as much detail.

When your flash is up in Manual Mode, your camera will probably give you minimal control over your shutter speed.  More than likely when your shutter is up your camera will set the shutter speed for you.  My camera in Manual Mode locks my shutter speed at 180th of a second.

However, I still have access to my aperture to control the light coming into my camera.  You can use this to fill in areas of really dark shadows on an otherwhise bright scene.

While in Manual Mode and with the flash up, meter the scene to what your camera tells you is correct.  For this scene it was

Shutter Speed 180th, Aperture f/8

Then stop down and see what happens to the image.  The image below was shot at f/11.

Keep stopping down.  f/16

f/19

f/22

f/27

f/38

Not every image is a winner, but at f/19 or f/22 we get a nice effect while using flash in brigth daylight.

Use this with people outside on a bright day.  Or if you have access to multiple people place the people at different depths with in the picture frame and notice how you can create depth by how far the flash will reach.


Categories: Flash