10 min read

All You Need To Know About Fill Flash

10 min read

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How you use fill flash is a question many photographers struggle with. Flash adds another level of complexity to photography. Like anything, once you have some understanding of how it works, it’s much easier than you might imagine.

You can make use of fill flash to enhance many of your photos and it’s not that difficult. In this article, I’ll introduce you to the basics of using fill flash and then guide you into a few more advanced techniques. You’ll see how easy it is to us fill in flash effectively.

What is Fill Flash Photography?

Some people ask, ‘What is a fill light in photography?’ It’s any light, a flash or otherwise, used to compliment another light source. It is often used to add light to shadow areas or when your subject is backlit. Fill flash is not used to overpower other sources affecting your subject. Instead, its job is to reduce shadows caused by stronger light.

When your subject is lit from behind this often results in it appearing too dark in photos. This is because the exposure meter reads the light from the background and not from your subject. By using flash you can balance the light on your subject with the light in the background. This way both your subject and the background will be well exposed.

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If you use flash but don’t control the amount of flash power, you may well over-expose your subject and cause dark shadows. We’ve all seen photos of people with a dark shadow cast on the wall behind them. This happens when the flash power is set incorrectly and too much light is emitted.

The essence of fill flash is to balance the output with the ambient light that’s affecting your subject. The key to finding the balance is in setting your exposure for the ambient light. Then your flash power to a suitable level relative to your exposure settings.

Sometimes your camera and flash will balance the exposure on your subject automatically. At other times the flash may be too bright or not bright enough. In these situations, it’s best to have a clear understanding of how to control your flash and exposure manually.

Young woman in a field lit with fill flash.
I made my exposure reading for the grass in the background and over-exposed slightly. My flash was on a stand with a small softbox. Nikon D800, 105mm f/2.8, 1/160 sec, f/3.5, ISO 100, Manual Mode, Pattern Metering, SB900 off camera. © Kevin Landwer-Johan

Understanding Ambient Light and Fill Flash

When you understand what’s happening with the light and how your camera manages the exposure, you can create photos with added depth and dynamic. Using fill flash can enhance the feel of your photos. This is because you’re in more control of how the light affects your subject.

If you’re new to using flash and are not sure why or how to make your camera flash, I’ll explain. Then I’ll get into how to balance the ambient light with your flash.

The flash icon on your camera looks like a little lightning bolt. It may be set to pop up and fire whenever the camera perceives the light to be too low to take a photo. It could be set never to fire. There are various other settings depending on your camera model. It’s best to research what they are and understand what each of them does.

young woman at a temple at night.
Fill flash at night. Nikon D800, 35mm f/1.4, 1/250 sec, f/1.4, ISO 400, Manual Mode, Spot Metering, SB900 off camera. © Kevin Landwer-Johan

While learning to use fill flash the easiest setting option is TTL. Using this setting the camera and flash communicate with each other and manage the amount of light the flash emits when you take a photo. These calculations are based on the amount of ambient light and your exposure settings.

If you have your exposure set well for the conditions, your flash will provide enough light to fill in shadows caused by the ambient light.

When you have your camera set to underexpose the ambient light, in TTL mode your flash will compensate by putting out more light when it fires. This may result in more contrast and a dark shadow being created by your subject.

Setting your camera’s exposure to overexposing the photo will mean the flash outputs a minimum amount of light that might not be visible in the photo.

Couple in a n empty carpark.
I set my flash power so it would not affect the background, only the couple. I also darkened the background during post-production. Nikon D700, 35mm f/1.4, 1/320 sec, f/2, ISO 200, Manual Mode, Pattern Metering, SB800 off camera. © Kevin Landwer-Johan

Manual Flash – When and Why

Very often your camera and flash will automatically provide a nice balance of light for your subject. At other times you might experience too much or too little flash on your subject. In these situations, it’s good to have an understanding of how to use your camera and flash to expose your photos manually.

Your camera is pretty smart at controlling the exposure. Coupled with a flash it can often automatically provide a nice even light on your subject and balance it with the light in the background.

The problem with your camera and flash is they are programmed to function in a specific way. They never know what you are photographing or how you want your subject and the background to look. The technology is smart, but it is not creative. You are.

Woman on the train.
I set my flash and exposure so the background would be slightly darker. Nikon D700, 35mm f/1.4, 1/80 sec, f/2, ISO 400, Manual Mode, Spot Metering, SB900. © Kevin Landwer-Johan

This is why you need to control both your camera’s exposure settings and your flash settings manually. Learning to do this gives you the freedom to be more creative with how you light and expose your photographs.

High contrast conditions or when your subject has a strong backlight are challenging. The automatic settings on your camera and flash might not provide you with the style of photos you want. Light coming into your lens is more challenging to expose well. The camera will rarely manage auto-exposure well in these circumstances.

Being in control of your shutter speed and aperture settings manually allow you to balance your exposure with the power of the flash.

It takes time and practice to master, but it is worth persevering with. Learn to understand the principles of balancing the light to achieve the exposure you want. Then you’ll unleash so much more of your creative potential as a photographer.

flaming cocktails with fill flash.
Precisely the right amount of flash output was needed or the flame would not be visible. Nikon D800, 105mm f/2.8, 1/80 sec, f/3.2, ISO 5000, Manual Mode, Spot Metering. © Kevin Landwer-Johan

Aperture, Shutter Speed, and ISO Choices

The aperture, shutter speed, and ISO settings affect your exposure. The power setting your flash is set to also influences exposure. It’s important to understand how these settings are related.

Adjusting the shutter speed when using a fill flash does not influence how the light from the flash affects the exposure. This is because the duration of the light from the flash is shorter than the amount of time your shutter is open.

Every camera has a maximum speed the flash can synchronize with. This varies between cameras and flashes but is normally about 1/250th of a second. If your shutter speed is set faster than this your camera might automatically adjust it, even when you’re in manual mode.

When you take a photo using fill flash and your shutter speed is set faster than the sync speed, part of your photo will be black. This is because the shutter begins to close and blocks the light from the flash.

Altering the aperture and the ISO settings will affect how much light you need your flash to produce to obtain a good exposure. Using a wider aperture or a higher ISO, you’ll need less power from your flash. When you set a narrower aperture or a lower ISO, your fill flash will have to be brighter for a well-balanced exposure.

So when using fill flash you need to think a little differently about your exposure adjustments. Remember your shutter does not affect the exposure from the flash, but it does still affect how the ambient light looks.

Thai flag at Wat Chedi Luang.
To capture the movement of the flag I used a slow shutter speed. I took my exposure from where the flood light illuminate the chedi and balanced the flash exposure which was aimed at the flag. Nikon D800, 35mm f/1.4, 1.3 sec, f/4, ISO 100, Manual Mode, pattern Metering, SB900 off camera. © Kevin Landwer-Johan

Outdoor Photography With Flash

Using flash for outdoor photography does not make sense to many people. Most people think that when there’s plenty of light you don’t need to add more. Adding a little flash fill to an outdoor photo can make a big difference.

Flash photography outdoors helps to reduce the brightness of the hard shadows the sun produces on your subject.

Adding flash to an outdoor portrait, for example, can reduce or eliminate shadows in people’s eye sockets and under their noses and chin. Even softening these shadows by using flash, the lighting becomes more attractive.

If you’re using the built-in flash on your camera, outdoor flash photography might not be so successful. This little flash will not be so powerful and might not compete well with sunlight. When your subject is small enough and close to you, you’ll be more successful.

Using a larger, external flash with more power gives you more opportunity to use fill flash outdoors.

woman and baby elephant photo lighting with flash.
Elephant skin absorbs a lot of light! I added some flash to lighten the elephant a little. Nikon D700, 35mm f/1.4, 1/100 sec, f/4.5, ISO 100, Manual Mode, Spot Metering, SB900. © Kevin Landwer-Johan

On-Camera vs Off-Camera Fill Flash

With an external flash, you have the option of not mounting it on your camera. Being able to choose the direction the flash fill comes from can help determine the look of your photographs.

Direct flash is limiting in that you are restricted to light from your flash providing fill only from your point of view. Filling in a strongly backlit subject is often sufficient. When the ambient light is strong and coming from the side or behind you, it’s good to position your flash so it’s opposite the light. This will fill in the shadows more effectively.

This type of flash use might require additional equipment. Some compatible cameras and flashes can be used together, such as the Nikon Speedlight system. With other brands, you might need a trigger for your flash so it can connect remotely with your camera.

Some popular brands of external flash triggers are Pocket Wizards, Godox, and YONGNUO.

young woman photographer using flash.
My flash was on a stand with a small soft box to provide fill light coming from my left to reduce the shadow on her face. Nikon D700, 105mm f/2.8, 1/250 sec, f/3.5, ISO 100, Manual Mode, Spot Metering, SB900 off camera. © Kevin Landwer-Johan

Modify Fill Flash for Natural Looking Photos

Using a diffuser or bouncing your fill flash off a reflector of some kind produces more natural-looking lighting.

Lighting direct from a flash is harsh because the size of the flash head is so small. By Diffusing the light this scatters it and makes it softer. For flash portraits, this is often much more appealing than high contrast.

Popular diffusion techniques include bouncing flash off a ceiling or nearby wall. Small softboxes can be mounted on a flash and these do a great job of diffusing the flash, but they can be a little cumbersome.

A quick online search will reveal all kinds of attachments you can buy for your flash to help you manipulate its output.

Whenever diffusion is introduced, you have to compensate for lower flash illumination. Do this by adjusting your exposure sufficiently. You can do this by increasing the power output from your flash or opening your aperture setting. Choosing a higher ISO if you need to can also help.

smiling woman in a garden.
Soft, balanced fill flash creates natural looking lighting. Nikon D800, 35mm f/1.4, 1/160 sec, f/3.2, ISO 100, Manual Mode, Spot Metering, SB900 off camera. © Kevin Landwer-Johan


As often as possible I’ll use my flash externally and also diffuse it. I prefer this look for my photos.

Being able to direct the flash so it’s opposite the main source makes for a more interesting and often more natural feeling. Always having it mounted and coming from the same point of view can produce mediocre results.

Lighting that’s scattered by some form of diffusion is soft and often more pleasant. There are times when you’ll want a high contrast look and these are times direct flash is perfect.

Poi Sang Long Festival photo using fill flash.
The early morning light was flat and dull so I used some fill flash to help add some pop so the photo matched the excitement of the festival. Nikon D800, 35mm f/1.4, 1/20 sec, f/5, ISO 100, Manual Mode, Pattern Metering, off-camera flash SB900. © Kevin Landwer-Johan

Take time to practice. Study how your equipment works and how your flash and camera are related. Understanding how to manage your flash externally will take some commitment, but it’s a great skill to have.

If at first, it doesn’t make sense, keep experimenting. Photograph the same subject in different lighting situations, with and without using your flash. Compare how the photos look and think about how you can improve them. Then go and try again.

Mastering fill flash is well worth it. Your photography takes on a whole new dynamic when you are more in control of the lighting. Being able to control its power and position means you’ll be able to give your photos the look and feel you want for them.

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Kevin bought his first camera in the early 1980s and started working in the photography department of a daily newspaper a few years later. His whole career is focused on photography and he’s covered a multitude of subjects. He loves to photograph people the most. During the past decade, Kevin has begun to teach and write more, sharing his passion for photography with anyone who’s willing to learn.
Kevin bought his first camera in the early 1980s and started working in the photography department of a daily newspaper a few years later. His whole career is focused on photography and he’s covered a multitude of subjects. He loves to photograph people the most. During the past decade, Kevin has begun to teach and write more, sharing his passion for photography with anyone who’s willing to learn.

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  1. I was looking for a way to get the natural looking photos, Thanks your post has helped me a lot. I wish I can use the technique practically.

  2. Hi John, I’m pleased to know that my article helped you. It definately takes practice. The more you try and experiment, the better you’ll become.

  3. I’ve decided to try using fill flash for some outdoor shots when the light is not good. I’m in the U.K. and we have a lot of dull and overcast weather. So I’ll make a start with outdoor portraits using my Leicaflex SL cameras and 100mm f4 lens with the Metz CT45-1 manual flash. I can vary the flash output and by using it on this old camera that doesn’t have any electronic equipment in it, the high voltage of the trigger won’t damage the camera.
    I’m sure it will brighten my subject and add a new dimension to my photography.
    I wanted some basic advice and I got it from this site. Thank you.

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