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Once new photographers wrap their heads around how light direction impacts an image, the next logical step is controlling light. And that’s where fill light comes in.

It may sound like it, but don’t think that fill light is something for flash photography only. Far from it! Natural light photographers use fill light just as much as strobe photographers. It’s just different.

That’s the great thing about light – there are so many ways you can use it to create a look, a feeling and tell a story.

Fill light can be as complicated or as simple as you like. In fact, you probably already know about it, even if you think you don’t.

What is a key light ?

Before we can get into the details of fill lighting, we need to first look at what is a key light.

A key light is just another way of saying main light. 

So, for natural light photographers the main light is the sun. For flash photographers the key light could be the sun or their flash (either on or off camera), depending on how they use it.

Every photo needs a key light, but not every photo needs a fill light. But don’t let that fool you into thinking it’s not that important – here’s why… 

Fill light created by reflected light of the sand

What is fill lighting?

Fill light is any light that is less bright than the key light and is used to fill in the shadows caused by the key light. It doesn’t even have to be an actual light, but we’ll get to that in a moment.

In the studio you have complete control over all light, so you set your main light at whatever brightness you want and then the fill light less bright. Again how bright or dim the fill light is depends on the image you want to create. This is what’s called a two light set up.

When using off camera flash outdoors you can use the sun as either the main light or the fill light, depending on time of day and the power of your flash lighting.

In natural light photography, the main light is always the sun, but that’s not the only light available to natural light photographers. Fill light can be reflected light.

What is reflected light?

Again, the clue’s in the name. Reflected light is any light that is reflected back onto the subject.

You can create reflected light with:

  • A reflector – either one you bought or something you made
  • A white wall
  • The ground, such as beach sand (like in the image above), gravel, even grass
  • Any shiny surface, including water
  • Light coloured clothing

Further reading: How to use a reflector properly and why you really need one

In photography, anything that reflects light back onto the subject is a reflector. 

Just be careful about the color of the object that’s reflecting light. If it’s green, for example, the light bouncing off it will be green, which then casts a green light over your subject.

This is why when you photograph on grass in midday sun your subjects end up looking a bit green.

Fill lighting created with white side of reflector

For these photos I hung my reflector from a tree slightly to camera left. In the image above I used the white side of the reflector, which has a matte finish. In the image below I used the gold side, which is much brighter and more reflective than the white side. The color is too yellow, the light is too harsh for the photo and the shadows are all wrong – her neck is brighter than her forehead.

Fill lighting from reflected light of gold reflector

What is fill light used for?

Sometimes it’s as simple as it sounds – fill light is for filling in the shadows:

  • If you don’t want deep shadow in your image, you need fill light
  • To soften hard shadows, you need fill light
  • When your subject is lit from behind (backlit), you need fill light

Fill light, despite playing second fiddle to the key light, is actually just as important for creating atmosphere.

How much fill light you use can completely change the mood of a photo by changing the shadows. Consider:

  • dark and moody – with lots of deep shadows
  • light and airy – with very little shadow

Further reading: How to use shadows in photos to add atmosphere

What kind of light is good for fill light?

Any light source can be used for fill light. What matters is that the light must be diffused.

Fill light needs to be soft light, because its job is to fill in shadows. If it were a hard light, it could end up creating shadows instead.

Natural light is diffused when it’s:

  • not shining directly on the subject, for example when the subject is in the shade
  • reflected off a non-shiny surface, such as a white wall
  • Partially blocked by thin material, such as net curtains

Flash can be diffused by:

  • Using light modifiers such as softboxes or umbrellas
  • Bouncing the flash light off a non-shiny surface, such as a wall, onto the subject

What’s the difference between hard light and soft light?

Think of your shadow on a very bright sunny day versus your shadow on an overcast day.

On a sunny day the light is hard, so the transition between light and shadow is sudden. This is hard light.

On an overcast day your shadow isn’t clearly defined and the transition from light to shadow is much more gradual. This is soft light.

Further reading: Why you need to know about light quality

Natural light photography with no reflector

Here no reflector was used, so there is shadow on her face. As it was an overcast day the light was very diffused so the shadows were soft.

Where should you place a fill light?

To answer this, we go back to direction of light, because it’s not just about the direction of the main light. Fill lighting direction is also very important.

Further reading: Understand light characteristics for consistently great photos

Behind camera

In portrait photography, the fill light position is very often behind the camera to flood an even flow of light into the scene’s shadows from the front, especially when the subject is backlit.

Portrait photography lighting with no fill light

In the above photo no fill lighting was used, but in the image below I placed fill lighting behind me. I wanted shadows, but not as deep as in the image above with no fill.

Portrait photography Lighting with fill light

To the side of the camera

When placing a fill light to the side of a camera, it should ideally be on the same side as the main light – on axis with the lens when using side lighting. This avoids conflicting shadows falling on the subject.

Below the camera

Although we’re used to light coming from above, so your main light should never be positioned below your subject shining up, a fill light can.

In fact fill lighting is very often placed below the subject in portrait photography so that the light fills in the shadows beneath the chin. Clamshell lighting is exactly this – the main light is placed in front of and above the subject with the fill light in front of and below the subject. It’s a classic portrait lighting technique for beauty photography.

When the fill light is below the subject it’s particularly important to make sure that the it’s not as bright as the main light.

This lighting cheat sheet will help you with thinking through lighting direction.

Flat lighting and fill light

The two times that fill light is as bright as the main light is when you:

  • create a high key image
  • want flat lighting

The aim in both instances is to have as little shadow as possible on the subject.

Fill light in high key lighting

A high key lighting set up in the studio with the fill light set equal to the key light.

Further reading: What is high key photography, and how to master it

The first portrait photographer that springs to mind when I think of flat lighting is Sue Bryce.

She’s predominantly a natural light photographer who has perfected the art of flat lighting her subjects using diffused light as a main light and reflected light for fill.

What you wear affects fill light

Photographers don’t wear black just as a fashion statement.

Black absorbs light, so if you wear black while photographing, you won’t run the risk of light bouncing off your clothing back into the subject. If it did, you’d be creating fill light.

That said, when photographing newborns using natural light in my clients homes I’ve often worn white to maximise available light in the room by reflecting it back to the subject to lighten shadows. 

See, anything can be used as reflected light for fill!

What is negative fill?

Just when you thought we were done with fill lighting, here’s a twist – negative fill.

It’s the opposite of adding in light. With negative fill you use something black near your subject to absorb the light and therefore increase the depth of the shadows. 

It could be any non reflective black material, such as black cardboard…even the black shirt you’re wearing if you’re photographing up close to your subject.

Wrapping up fill lighting

Every photo needs a key light, but not every photo needs a fill light. However, when it is used, it has a huge impact on a photo – both good and bad.

The more you develop your photography skills, especially lighting, the more you’ll find yourself focusing on fill light and all the creativity that it opens up. 

What I love about light is that you don’t need to know everything all at once. You can build up your knowledge in blocks until, eventually, you’ve got a thorough understanding of just how important and wonderful it is!

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Fill light is an essential lighting skill for natural light photographers and flash photographers. Once you\'ve mastered the basics of lighting, you need to know how to use fill light for drama and atmosphere for flash and natural light photos that wow! Learn about using fill light vs key light and how they work together to create completely different images in seconds. #photography #lighting #fillight #flash