Lighting 102: Apparent Light Size

Abstract: It's not how big your light is, it's how big your light looks to your subject.

This is Gary. Gary is a snail. And he's beautifully lit by my friend Sara Lando. While babysitting Gary for a friend, Sara decided to actually build a miniature set and then photograph the snail in the style of Irving Penn. Because this is what creative people do in their spare time.

And pray tell, what beautifully soft light source is she using to subtly caress Gary and reveal his form?

Oh look, it's a bare speedlight:

How can this be? Aren't bare speedlights all hard and unflattering?

Not to Gary, because Gary is tiny. So to Gary, the speedlight actually looks pretty big. And when it comes to soft light, how big the light looks is what really matters. And how big a light looks is a function of the size of the light, and the distance from the subject to the light.

So for Gary, a bare speedlight—about three inches away—turns out to be a soft, flattering light source.

Could you light a person with a bare flash and get soft light? Yes... sort of. You can do it, but just not the whole person at once. More like, you could light their eyeball in a flattering way with a bare speedlight. Because a bare flash is gonna have to be an inch or two away from something to look like a soft light source. (To be clear, I do not recommend photographing eyeballs in this manner.)

And that is the whole thing in a nutshell: softness is not just about how big a light source is. It's all about how big the light source appears to the subject. Which is a function of both physical size and distance.

Is the Sun a Soft Light?

Direct, undiffused sunlight? Nope, the sun is not a flatteringly soft light source.

But it's big, right? Almost a million miles in diameter. That said, it is also almost 100 million miles away. So it appears to us as a hard light source.

Stick some clouds in font of it — way smaller, but waaay closer — and boom, soft light. It's all about how big the light source looks to the subject, from the perspective of the subject.

Is an Umbrella a Soft Light?

So what about our basic umbrella. Is it soft?

Yes it is, so long as you don't light from too far a distance. From 3 to 6 feet away, an average size photo umbrella looks pretty soft. It's softer when you are in closer, and harder when it is further away. From 18 inches away, an umbrella is downright magical:

For very flattering headshots, some photographers will move the umbrella right up to the subject, until it starts to appear in the photo, then back it off just a bit. Remember when I said I did this a lot? That's why.

But what else happens when you move a light in close? It falls off more quickly, right? I also find that useful for headshots, to help me control my background.

And that is the equation you have to balance. Softness vs. evenness. Physics giveth, physics taketh away—or in this case, physics giveth twice.

No, actually make that thrice. But we are not there yet.

Can you have both softness and distance at once? Sure you can. Just crack open your wallet and spring for a giant Octa bank light source. Typically, they are circular (-ish, it's an octagon) and five or so feet across. But they cost a pretty penny, and they need much more flash power to make up for all of that diffusion and extra working distance.

Not to dispair. You can do a lot of cool stuff with your $30, 43" double-fold umbrella. It's great for shooting people.

And more good news: since you now know to fill your shadows to make them legible, you are not dependent on the failsafe look of an expensive Octa to create soft, nuanced light.

Controlling the falloff into the shadows (by setting that legibility floor) gives you all the control you need to make the less expensive version of soft light work for you.

Next, let's take a look at how to get both control and predictability with your soft light sources.

Next: Understanding Soft Light


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