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Flash Compensation: What It Is and How It Works

9 min read

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Flash Compensation.
Quick summary

In this guide, we will take a look at flash exposure compensation, a powerful yet overlooked tool for fine-tuning the output of your flash unit to your tastes. We will discuss how FEC differs from conventional exposure compensation but also where the two share some fundamental similarities. Of course, you’ll also get to learn how flash exposure compensation works and how to use it to get the perfect flash output you’re looking for, with no need for guesswork.

Flash photography is a powerful tool that allows you to capture scenes that would be challenging if not impossible relying only on natural light. However, sometimes we find ourselves dealing with flash output that doesn’t match the composition we had in mind.

When this happens, it’s crucial to know how to adapt flash exposure to your own needs manually. The way you do that is via flash compensation, a handy feature built into just about every camera body and speedlight today.

If you’re still a beginner, you might be wondering how flash compensation works in practice. You probably also want to find out how to set it up and customize it to suit your shots.

Just that is going to be the subject of today’s guide. Let’s take a look at all the basics you need to know about flash exposure compensation, how to apply it, and how to use it to get a great flash exposure with each press of the shutter button!

Getting Correct Exposure With Exposure Compensation

Close-up view of the exposure comp. button on a contemporary DSLR camera. Exposure compensation is an essential tool for getting well-lit and properly exposed images.

Fundamentally speaking, flash compensation doesn’t differ so much from your off-camera exposure compensation system. That’s why we are going to take a closer look at how camera-based EV compensation works first. Understanding the principles behind it will make wrapping your head around flash compensation that much more straightforward.

So, what is exposure compensation for? The simple answer is that it is a mechanism to quickly adapt the overall exposure of your scene. This works completely independently of manual exposure settings! In any automatic exposure mode, EV compensation is only a flick of a dial away and holds immense power.

By changing the balance between all camera-controlled settings, which can include shutter speed, aperture, and even ISO, exposure compensation lets you adjust the luminance and overall exposure levels of your shot with ease.

An example of exposure compensation in action. Rocks by the seashore exposed in daylight.

Let’s analyze a simple theoretical example of exposure compensation in action. Say you’re setting up a portrait shot in aperture priority mode. You might see that opening the lens up to your desired f-number results in blown-out highlights and washed-out skin tones. Now, one way to resolve this would be to go back to manual mode and tinker with shutter speed and ISO settings to balance this out.

However, the exact same results can also follow from dialing in a modest negative number on the exposure compensation dial. This will tell your camera to override the values given by the metering system to get the correct exposure you’re looking for.

Positive EV compensation values are good for bringing out light elements in your subjects when they’re under-exposed. Negative exposure compensation helps when shadow areas and blacks appear as muddy greys.

Flash compensation works in much of the same way – with some crucial differences, we are going to explore below.

Flash Exposure Compensation (FEC): How it Works and What it Means?

A monochrome portrait of a male model. High contrast shows the necessity for proper handling of EV and flash exposure compensation.

Put in a nutshell; flash exposure compensation is exactly what it sounds like. Taking the same principles you know from in-camera EV compensation, the flash compensation setting manually changes the output of your flash gun in small increments. This works on the fly with almost all modern TTL flash units. There’s no need to go into manual flash mode and calculate flash power the old-fashioned way!

Flash compensation can be incredibly useful when dealing with high contrast scenes. Your camera metering system determines the optimal flash output mostly based on a so-called “middle gray” light value. When elements in your frame are too far off from that middle gray – think white textiles, reflective surfaces, dark skin – you might need to nudge your flash exposure this way or that way.

Of course, adjusting the flash power has a different effect on your final image than playing with your camera’s fundamental exposure settings. You will see that higher FEC values expose the subject more, separating it from the background. Lower flash output exposes your subject less whilst having little effect on background rendition.

In this sense, you may think of FEC as a more narrow application of standard exposure compensation. There’s one major difference though: the latter adjusts the exposure of the whole scene. Meanwhile, using flash exposure compensation only really affects the area covered by your flash units. In all likelihood, that’ll be your subject or group of subjects. So, in practice, flash compensation really works like a fine ‘subject override’ for overall exposure compensation.

To access flash exposure compensation, most cameras employ a dedicated button located on the back panel not far from the EV compensation switch. Look for a lightning bolt icon, and change the exposure compensation value with the camera’s command dial.

Setting Flash Output Via In-Camera Exposure Compensation

Close-up view of the exposure compensation dial of a modern digital mirrorless camera. Plenty of camera models nowadays allow you to control both EV compensation and FEC via the same dial.

Here comes the confusing bit. On many cameras, especially Nikon gear, you might find that tweaking the EV compensation dial on the back of the camera body automatically adjusts flash exposure compensation as well. That’s right – just by the main dial, you can regulate both flash compensation and ambient light exposure compensation.

This can work great if making small edits to your exposure is what you’re after. Not having to head over to your camera’s hot shoe for separate settings streamlines the ergonomic experience a tad. It allows you to focus on the end result – brightness, or lack thereof – instead of worrying about how to get there.

However, there’s a flip side to this as well. When you don’t want it to, having your EV compensation cover both in-camera exposure and flash compensation can be annoying – if not outright limiting!

Thankfully, there is a way to set your camera’s exposure compensation to split the two control options.

Within your camera menu dialog, look for an FEC setting called ‘FEC Background Only’. This should completely disconnect exposure compensation from flash compensation functions, allowing you to adjust both independently.

Making Fill Flash More Versatile With FEC

Still life of vegetables in a basket and on a wooden surface. Skillful use of fill flash exposure compensation created a moody, low-key look.

One possible use case for flash exposure compensation that can make a real difference in your professional photography is improving the effectiveness of fill flash. Especially when using your camera’s built-in pop-up flash unit, it can be very difficult to get a correct exposure purely through TTL flash mode.

This is because your camera’s metering system expects normal flash output to fill the whole frame as much as possible. The standard algorithm calculates flash exposure such that no regions end up under-exposed. This makes shooting indoors at default settings often go against the purpose of using fill flash in the first place.

You can configure your fill flash output via flash compensation to mitigate this. Dial down the flash exposure compensation to a moderate negative number. Depending on the ambient light, anywhere from -0.7 to -3.0 could work fine. Make a few test shots in quick succession to compare the different flash exposure settings!

By trimming your flash power in this way, you can use fill flash in the truest fashion to fill in spots of low exposure without hurting the look of your image.

Giving Bounce Flash More Power Through Compensation

Portrait of a young model wearing reflective plastic designer clothing. Challenging lighting and bounce flash make flash compensation very useful here.

Bounce flash is one of the greatest aces you can have up your sleeve as a photographer. It allows you to challenge and circumvent complex lighting situations, especially indoors.

You can make an ounce flash act as a fill flash. Especially when you are working with a variety of light sources, bounce flash can gently ’round out’ corners and edges, giving a smoother appearance.

However, bounce flash is quite a bit more versatile than just that!

Shooting portrait photography, you can bounce your flash off the wall to highlight your subject’s most flattering facial features. Or, you could dial it up in a candid shot to make sure the background is at the perfect exposure level relative to the centerpiece of your shoot.

You can gain much greater levels of control over the capabilities of bounce flash using flash compensation.

For portraits, know that flash power might be a bit on the high side. This is because bounce flash will try to ‘fill in’ as much as it can to even out your exposure, which may not be what you want. To achieve more nuanced-looking pictures, consider dialing it down by at least 1/3 EV.

On the other hand, dealing with tricky indoor environments where there are no strong ambient light sources around, normal flash output may not be enough. In this case, add exposure compensation to really make your subjects shine!

Using Flash Exposure Bracketing to Find Your Optimal Exposure

Again, I invite you to practice flash exposure bracketing in any case of doubt. That is, create a series of the same composition executed using a different amount of flash compensation for each frame.

Each of the resulting shots is called a ‘bracket’. Practicing flash exposure bracketing helps you be more secure in your photography as it allows you to see the different effects of varying flash compensation settings first-hand. Just pick your favorite pictures out of the pile, and over time you will develop a sharp sense of which flash exposure settings work best!

This is not just a great technique to use when you’re fussing over what kind of flash power to use for bounce flash. It also works exceedingly well in almost any context where fine control over flash compensation can make a significant difference in your images.

Flash Exposure Lock

Portrait of a dog in low-key lighting. Moody studio shot taken with fill flash exposure compensation.

If you’ve been reading up on camera settings in-depth, you probably have already come across the Exposure Lock feature found on your camera body. In normal operation, your camera’s light meter continuously updates its readings many times a second. This means that any automatic exposure settings will be adjusted by themselves if you re-position your viewfinder, for example. Exposure Lock lets you override this behavior and keep the exposure settings picked by the meter from a certain time stamp.

Flash Exposure Lock follows a similar idea. When using an automatic flash exposure mode on e-TTL and i-TTL flash units or similar gear, it lets you force the flash metering system to keep using the current flash exposure setting even if readings change. Because flash metering is mostly based off of ambient light and subject distance, this opens up the door for plenty of cool and unique flash applications that would otherwise only be possible in manual flash mode.

However, because metering for correct flash exposure is notoriously sensitive, it’s very likely that experimenting with this feature will run you into a few brick walls. Even with the nicest TTL flash gun, using Flash Exposure Lock may provide you with poor flash output and mismatched subject coverage.

You can easily add exposure compensation to your locked flash output to correct this. Over- and underexposed subjects can easily be adjusted and brought more in line with your creative vision this way.

Note that with most cameras and flash units, activating FEL will prompt the flash to fire first in order to take an accurate reading of your target. However, this does not release the shutter by itself.

How Using Flash Compensation Can Help You In Professional Photography

Professional photographer composing with flash unit mounted on camera.

Flash compensation is one of those overlooked features that help you achieve your creative goals in countless subtle ways. Yes, it’s a neat way to fine-tune flash exposure and get the brightness output you want. But flash exposure compensation is also a lot more than that!

Given the skill and careful control, it’s a tool to elevate your photography and open up a whole world of possibilities for your expression. Using compensation for your flash exposure helps you create much more deliberate and complex images than what going off of automatic e-TTL flash alone would allow. It also helps you hone your creative compositional skills without having to switch over to manual flash shooting.

Flash compensation is also very flexible since you can use it in the same way as the regular in-camera exposure compensation system you’re used to. Depending on your camera model, you may even be able to link the two exposure compensation controls together!

Mastering flash compensation takes time, just like all good things in photography. But I am sure that, with the guidance and tips in this guide, you’ll have a solid chance to get to grips with it all in no time!

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Jonathan is a writer and photographer currently based in Poland. He has been traveling the world, taking pictures, and writing about his experiences for over five years. His favorite subjects include landscapes and street scenes.
Jonathan is a writer and photographer currently based in Poland. He has been traveling the world, taking pictures, and writing about his experiences for over five years. His favorite subjects include landscapes and street scenes.

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