Photography refers to the act of capturing light hitting an exposure medium to make an image. Whether by film or digital cameras, the foundation of photography exposure is always the same. Because of that, one of the most integral things all photographers strive towards is to perfect exposure – in other words, to perfect the amount of light that they capture.
Too much light, and we’re talking about overexposure. Too little light, and you have what’s called an underexposed photo. But how do you recognize when overexposure or underexposure occurs? How do you correct it? And where is the ideal exposure value in the first place?
All these questions are going to form the subject of today’s guide. Let’s take a look at everything you need to know about overexposure, underexposure, and everything in between!
Defining Overexposed vs Underexposed
To understand the problem of finding correct exposure, we first need to define it. As you might expect, the debate surrounding overexposure vs. underexposure is really about two sides of the same coin.
Too Much Light Kills Detail…
Overexposure in photography refers to an excessive amount of light hitting your exposure medium. When your camera sensor (or film) gets oversaturated with light, your scene appears brighter than in real life. The brightest parts of your image can become so overexposed that they actually become washed out, losing detail.
In an extreme scenario, a severely overexposed image can end up appearing as pure white!
…Too Little Light Obscures It
On the opposite end of the scale, underexposure occurs when your camera sensor lacks enough light to lend detail and definition to dark tones. Poorly-lit scenes will display very little detail in an underexposed photo, often appearing as near-black.
An underexposed photo can sometimes be hard to identify because brighter highlights will appear pretty well-defined and clear. However, watch out for the shadows!
In the example above, notice how most of the forest to the side of the railroad tracks features pitch-black shadows, completely missing texture, and detail. That’s the hallmark of an underexposed photo!
What is Correct Exposure and How Do You Find It?
Defining overexposure and underexposure is pretty easy, as you have seen. As long as you are familiar with the symptoms of each, you should have no trouble reliably identifying them in the future.
It’s actually much more challenging to narrow down the idea of ‘correct exposure‘. However, when do you know that you have neither under nor overexposed your photo?
There is one main objective standard that photographers use to determine how much light really is optimal for perfect exposure. Let’s take a look and see how you can easily tell whether you have correctly exposed your choice of camera settings.
The Concept of ‘Middle Gray’
The most widespread standard for correct exposure refers to a value called middle gray. Middle gray, in plain English, is the light value right in between absolute black and absolute white.
You’d be forgiven for thinking that middle gray is therefore equivalent to 50% exposure. It’s actually a lot more complex than that! In fact, there is no one proper exposure value that is universally recognized as ‘middle gray’. Instead, middle gray is somewhat fluid, depending on your lighting conditions.
This is because our eyes, or rather our brains, do not perceive light in a completely linear fashion. Your camera’s exposure meter is also not perfect in that regard.
Imagine photographing a perfect white subject that reflects close to 100% of the light that hits it. Now, add an absolute black object – one that absorbs pretty much all light. To this maximum-contrast scenario, add a ‘middle gray’ object that is halfway in between the brightness of both of these.
Because our eyes do not process exposure in a linear fashion, the 50% “middle gray” would not look exactly neutral to a human observer. In fact, it would look quite bright sat next to the absolute white! And that’s just where the problem lies. With different settings and different exposure values, you need to apply some compensation to get ‘true’ neutral-looking tones.
Therefore, it’s important to adapt our conception of middle gray on a case-by-case basis.
How Your Light Meter Sees the World
For most scenarios, photographers use a gray value of 18% to get an idea of proper exposure. This is the closest you can get to what our brain perceives as “in-between” mid-tones.
However, your camera’s light meter isn’t built exactly the same way as your own pair of eyes. To avoid the point where your image appears brighter without losing shadow detail, you have to actually apply even more negative exposure compensation.
The default number value that most professional photographers use is 12%. Actually, for the sake of precision, it should be 12.8. Still, most values between 12 and 14 should work with little trouble.
What to Do About Overexposed Photos
Knowing the relationship between light values and a properly exposed shot, what do you do when you have an overexposed image on your hands? Worry not, as there are plenty of beginner-friendly methods that you can use to fix overexposed photos. Let’s take a look at a few of them!
Select a Faster Shutter Speed
Unless you’re shooting fast action and one shot is all you get, you are probably able to take a quick second image under correct exposure settings to iron out any obvious flaws.
In this case, if you feel your photo came out overexposed, one of the easiest ways to quickly correct that is to dial up the shutter speed. Your shutter speed directly controls how much light hits your camera sensor, so it’s a foolproof way to reduce exposure.
If you’re not able to balance out an overexposed image with a faster shutter speed, remember your exposure triangle. A smaller lens aperture or lower ISO settings will also reduce exposure in the same way!
Use Exposure Compensation With Care
If you’re using an automatic exposure mode, such as aperture priority or program mode, then exposure compensation is an even more straightforward way of adjusting the exposure of your photo on the fly.
A stop on the exposure compensation dial perfectly corresponds to a stop of light value. That means that lowering EV by 1/3 on the dial provides the same results as going from an aperture of f/5.6 to f/6.3.
By comparison, EV compensation is a lot more of a “fire-and-forget” solution. It never requires you to deeply consider which side of the exposure triangle will be affected. Exposure compensation makes sure that everything stays in balance while still giving you a way to have direct control over the light value in your image.
Use an ND Filter to Ward Off Excess Light Hitting the Lens
If you need an immediate fix for an overexposed photo without changing camera settings, then an ND filter is your best friend. This handy lens filter uniformly lowers exposure across your whole frame by blocking a certain amount of light.
ND filters exist in many grades or strengths, suitable for basically any lighting conditions. They are basically indispensable when attempting low-shutter speed, long exposure photography in daylight. In such circumstances, no combination of small apertures and low ISO sensitivity will be enough to ward off overexposure.
But even in other contexts, such as daytime portraiture, ND filters can be extremely useful.
Post Processing: Some Basic Techniques to Get You Started
Nowhere during your digital photography workflow do you have more control over exposure than in post processing. Today’s photo editing software is more powerful than ever, and it allows you to easily manipulate your exposure triangle on your computer to get the light values you are looking for.
There are a few main ways that you can digitally “pull” your overexposed images – that is, dial down the light value of the frame after it’s been taken. Many kinds of post processing suites make this easy nowadays with a simple “exposure” slider that you can manually adjust.
Other than that, make sure to check the white balance and adjust as necessary. With the help of a gray card, you can fine-tune these values with ease. You might also want to manually adjust color curves, as this gives you greater control over individual areas of your image.
The brightest parts of an overexposed photo might not always be uniform, so it’s handy to correct, say, just the whites within a certain range.
Mind the Differences Between Digital Photography and Film!
Though the bulk of what I said here applies to any kind of photograph exposed on any medium, not everything works the same between a digital sensor and film. The biggest difference is in terms of exposure latitude. That is to say, film and digital photography exhibit different kinds of sensitivity to being pulled and pushed (having their exposure decreased or increased, respectively).
On film, pushing by as much as a handful of full stops generally won’t ruin your photo. With that said, if you severely overdevelop your picture, you might experience very little detail due to heavy grain.
On the other hand, a digital sensor won’t allow you to push the photo that far at all – you’ll overexpose it to the point of getting a white frame!
However, the reverse applies to underexposure. Film is very sensitive here, and if you don’t make sure it receives enough light to form a clear image, there’s not much you can do to save it. Comparatively, digital photographs resist underexposure much better.
This is why an often-cited exposure rule actually exists in two versions. For film, expose for the shadows, making sure that the dark areas in your image appear clearly visible. Possible overexposure elsewhere can be corrected in development.
For a digital photo though, you should do the reverse by exposing for the highlights. You can later bring out lost detail from the shadows in post-processing!
How to Prevent and Fix An Underexposed Photo
Many of the strategies we just looked at can also work wonders on an underexposed image, just as with an overexposed one. You’ll just need to remember to invert the steps, i.e., decrease the shutter speed instead of increasing it.
Also, note that due to the differences in latitude between digital and film that we just went over, saving an underexposed photograph in the post-processing suite of your choice is actually easier than trying the same on a hopelessly overexposed image.
Set Your Metering Mode Correctly
One area that I haven’t touched on yet is the importance of choosing the right metering mode. For example, in a scene with a very high dynamic range and stark contrasts, you might want to use spot metering to only grab a light reading from your subject, disregarding the background.
Make sure to read up on all the various metering modes that your camera supports, as well as their unique roles and recommended use cases. While you can always try to use EV compensation instead, there’s usually a lot less work involved if you can rely on your built-in light meter to begin with.
Grab More Light With Shutter Speeds and Aperture
Instead of stopping down your lens, a wider aperture is what’s necessary to grab more light and improve the look of underexposed photos. Note that a larger lens opening does mean a thinner depth of field, which may not always be what you’re looking for.
And on top of that, the lens you’re shooting with may not always be fast enough to even push your exposure that far! In such cases, you should consider letting up on the shutter speed instead. A slower shutter speed can lead to motion blur when shooting handheld. On the other hand, it also dramatically increases the amount of light hitting your camera’s sensor.
Consider shooting on a tripod or using in-body image stabilization if you have no choice but to revert to a slower shutter speed.
Use Higher ISO Settings
Your third option (apart from automating these judgments via EV compensation) is to use a higher ISO. Just like on film, ISO sensitivity is directly linked to noise, so make sure to not overstep the limitations of your camera’s sensor.
Generally speaking, anything between 50 and 800 is considered suitable for regular daytime use. ISOs of far over 1,000 are usually reserved for low-light photography and fast action. This is because noise artifacts become much more visible as you enter the four-digit range on most digital cameras.
Remember, though, that your useful range of ISO values depends greatly on your camera model. Full-frame cameras offer much wider sensitivity ranges than crop-sensor designs. At the same time, CMOS sensors generally deliver cleaner results than CCDs at higher ISOs, but CCDs may still win out in low-ISO contexts.
Managing Exposure Intuitively
Let’s bookend this guide with a piece of inspiration. The greatest skill that you should strive to acquire, through dedication and practice of course, is the ability to manage the exposure in your photography intuitively and without external assistance.
By skillful use of such tools as your camera’s exposure controls, EV compensation, metering modes, and of course the properties of your shooting environment, you should strive to create perfectly balanced, well-exposed images with every press of the shutter.
Don’t think that this is an impossible mission. Far from it! At the end of the day, exposure is a creative choice. You’re not always going to agree with your camera’s light meter, and that’s okay. You don’t always have to make sure your subject is lit in perfect middle gray, either.
What matters is that you are capable of forming a vision of how your photo should look, including the balance of light and dark areas within the frame. To then shoot that scene and have it come out the way you imagined it is the ultimate form of photographic success.
If you’ve made it this far, there’s nothing stopping you from achieving that success. Keep working on your craft, be patient, and most of all have fun shooting!
Extremely helpful–thanks so much.