Flash Photography And the Law

Did you know that there is a law that we should be aware of when we use our flash?

This law applies to ALL flashes; the pop up flash on your camera and the, usually more powerful, separate flash unit that works off of your hot-shoe.

If you don’t know about this law, it could seriously limit your ability to create a photograph.

If I could, I’d site the statute, but it’s not a law that has any legal basis.

As my high school physics teacher would have told you, “Sam’s no physicist”, however he probably would be amazed that I’ve learned to apply a law of physics on a regular basis to my work as a photographer. The law I’m referring to is a law of physics that applies to light, called the  Inverse Square Law.

In brief, the inverse law states that as the distance between a light source and an object doubles, the intensity of the light reaching the object quarters.

How could the ignorance of this law seriously limit your ability to create a photograph?

As an example, on a basic level, you need to be close  enough to your subject  so they are illuminated by the light  from your flash.

As another example, it helps us visualize the photograph before we make an exposure..

Learn To Use Your Flash

4 thoughts on “Flash Photography And the Law”

  1. The inverse square law ties together f/stops, shutter speed and iso into one neat package. Each is a give and take from the balance of exposure. Do the math…1×1.4= 1.4, 1.4×1.4= 2, 2×1.4= 2.8, 2.8×1.4= 4, 4×1.4=5.6…..keep going, you’ve got 8, 11, 16, 22, etc. The holy grail!

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