A Simple Explanation on The Inverse Square Law | Lighting 101

[@alex0589]

Hey, Pye. Ive seen and read a lot of explanations of the inverse square law and even though i already kind of get it i wanted to stop here and watch and i think yours is one of the best and simplest ive seen for beginners. Cheers.

[@robertdixon7689]

Bro., you are an awesome instructor!!! Not only are explanations layman friendly, your delivery is refreshing and voice is not monotone. I enjoyed it thoroughly! Thanks!

[@pavankumar-hk1ch]

people who hate math explain much better than others! great explanation !!

[@mubblemann]

If the flash light level on your subject is 100% when the flash is 1 meter away, it will half its power as you move the flash to each of the following distances - 1.4, 2.0, 2.8, 4.0, 5.6, 8.0, 11, 16, 22 etc. Bet those numbers look familiar don't they! That's because aperture halves the exposure at each of those stops too. Same principle.

[@Vincent112june]

Mubble Mann I like what you've said. But you've gotten it slightly wrong. It isn't halves or doubles. It's each of the numbers multiplied or divided by the Root 2 gets you up one or down one. Take a calculator, 1 * root 2 =1.412135 and so on. Then multiply again by the Root 2 and you get 2. Pie's formula will work well enough for the 1, 2,4,8,10,32. But what about the light loss to the side. What he's missing is say at 4' from the source and 2' off the line to the right or left and he's lost 6 stops of light, if the unit he's using is a foot. Either way, foot, meter or my royal Irish shinbone, Pythagoras constant (*/ by the Root 2) informs the relationships. Oh, that relationship works the other way too with those gigantic lights.

[@mrterry1756]

Mubble Mann That's exactly what I thought!

[@Bullybeef972]

Well, I"ll be....didn't realize it was that simple....Well done!

[@PeeHooo]

So if I want to keep roughly same exposure when move my light source twice as far I need to set my exposure 2 stops higher? I know that light quality isn't the same after that, but the amount of light hitting the subject should be same, right?

[@KentDuFault]

I know math doesn't lie. However, I do know, as a commercial photographer with almost 30 years of experience, that doubling the flash to subject distance does not cut the amount of light hitting the subject by a factor of 4 (as measured by a light meter).

[@payamjirsa]

Kent DuFault This is literally the entire point of the ISL. Doubling distance is equal to 1/2 squared (which is 1/4th the original power). Only lights that don't apply are high intensity focused lights (such as lasers). Flashes and other diffused light sources follow this law. But, feel free to look it up for yourself.

[@Sprenklefish]

So I gotta do math when I shoot with flash now? Bring the tape measure and the abacus????

[@BigWoody1963]

Not at all. You just need to move your light source far enough back so that you expose properly on everyone. Think of the family example he gave and the chart he showed. The rest you should be able to extrapolate, especially with a bit of practice.

[@Subverttech4]

I like pi man terms o.o thanks :D

[@TimZarra]

yay Colliers

[@SUPERLIMINAL]

It took your host exactly 3 minutes before the explanation actually began. Before that the same information was repeated three or more times intermingled with cheesy quips. Makes for a very frustrating video to watch.

[@BigGoucho]

There is nothing worse than turning up to a shoot and having to do meth....