Tim, you’re doing a great job explaining this stuff in a way that we can understand it. All you professionals, you are also doing a great job NOT explaining the stuff in a way that’s easily understood. Remember, this “Portrait Lighting FOR BEGINNERS”! Again, Tim, thanks for explaining the concept in an easily understood manner.

When a light get further away, it does indeed spread out. However, most of that spread out light doesn’t hit the subject, so no, it’s not softer.

However, when a light is up close, it’s hitting the subject from more angles, thus wrapping around the object more and making the lighting softer.

Try it! Get a light and umbrella (or just a lamp and a lamp shade). Move it super close to an object in a dark room. Now move it ten feet away. Ignoring the difference in brightness, you’ll see that indeed the lighting is harder when it’s further away.

It seems to me the Law number 2 above is reversed.
The same intensity of light farther away seems softer the when moved in closer to the subject.
If it is farther away it would spread out more, making it softer.

When we put a mirror where the wall is and move the lamp in the same manner as before, this time the brightness of the spot we see in the mirror does NOT change, although we still see the image of the lamp in the mirror get bigger, which results in increased *total* light getting to us from the lamp. But the image of the lamp in the mirror is the same brightness whether it is close to the mirror or far away – it’s the same brightness as the lamp itself.

Total light is not the same thing as brightness – brightness is rather a measure of light density, that is, the amount of light *per unit area*.

Walls, and your polystyrene boards, exhibit mostly diffuse reflection, which means light hitting them from one direction is reflected in multiple directions. In the case of a mirror or shiny metal, the light hitting it from one direction is all reflected in a single direction – that’s a direct (also known as specular) reflection.

Another way to think of the same effect, if you are taking a photo of several identical candles viewed in a mirror, where some candles are significantly closer to the mirror than other candles – the spots from all the candles will be the same brightness! But the closest candle casts a much larger image. (Same as if the candles were photographed directly, without the mirror.) But if there is a painted wall behind the candles, how far each candle is from the wall will affect how bright a spot the candle casts upon it.

This also applies when photographing metals. If the lighting creates a highlight that is unacceptable due to being too bright – moving the light in a straight line further away from the metal won’t fix it. Rather, one has to actually dim the light itself or put something in front of it, or move the light so it’s at a different angle where it doesn’t create the unacceptable highlight at all. (Another option may be to use a dulling spray on the metal, making its reflection less specular and more diffuse.)

The book “Light: Science and Magic” by Hunter, Biver, and Fuqua explains all this in even more detail.

I’m not entirely sure I agree with you. I do film lighting, so I understand the principles if lighting quite well. The idea that and object doesn’t appear brighter because it’s a diffused or bounced source is quite confusing to me.

Lets say we have a polystyrene board that has a light source directed on it which is then bouncing at the subject. If the DoP told me the subject needs to be brighter, one of the first things I do is move the move the light source closer to the polystyrene board. D.o.P. is usually happy with the change.

Maybe I just misunderstood what you meant.