In this article, we discuss the topic of underexposure and overexposure in photography, with image samples and other relevant information for beginners. Now, on one hand, there’s not much to actually discuss – a simple explanation of the terms is what interests most beginner photographers. But here is my slightly-absurd-at-first-glance introduction to the article – there is no such thing as under- and overexposure. Dead serious.
Still, before we get all philosophical, understanding the two basic terms is quite necessary, if not for your creativity and ability to come up with gorgeous, moving, brilliant photography, certainly for being able to communicate with fellow photographers (I promise, we are not as boring as it may sound).
Table of Contents
Understanding the Terms
As you may already know, there are three things that influence the “brightness” of an image in any given level of light – aperture, shutter speed and ISO sensitivity. Of these three settings, aperture and shutter speed are the only two that actually let you gather more light in the field, which is why they form your exposure.
When trying to achieve a “correctly-exposed” image, what matters is not the settings you choose, but their correlation, as each of the three individually have an effect on the said brightness. So, for example, if you are in a brightly-lit environment and choose to use a wide aperture setting (say, f/2 or f/1.4), you will need to compensate it with faster shutter speed and/or lower ISO sensitivity value. Should you make a mistake and get the correlation between the settings “wrong”, you will end up with an image that is not exposed “correctly”. I will explain the quotes later on. For now, this is where the terms come in.
1) What is Underexposure?
An underexposed image is the sort of photograph that one might consider to be too dark. Here is a good example of such a photograph:
Note that this particular image was exposed differently upon capture – I altered its “brightness” using software, but it is fully representative. It’s clearly very dark and shows very little detail, only the brightest parts are easy to make out. Most importantly, it just feels wrong.
2) What is Overexposure?
Overexposure is the complete opposite of the previously defined term. An image that is brighter than it should be can be considered overexposed. When too much light is allowed during exposure, the result is an overly bright photograph. Just so you can easily compare, here is the same photograph I showed moments ago, but rather than being underexposed, it is overexposed:
See the enormous difference? Where the previous image sample was much too dark, this one is much too bright, to a point where it is unpleasant to look at. It is just as lacking in easily-distinguishable detail, too, and does no justice to the highlights or shadows of the objects captured.
3) What is Correct Exposure?
This is perhaps the most obvious and self-explanatory case. Correctly exposed image is the one that feels just bright or dark enough so that both the shadows and highlights are as they feel the most natural and comfortable to look at. Theoretically, such a photograph contains no lost highlights or shadows, meaning all the detail is clearly distinguishable and as close as possible to “real life”. The following version of the image sample can be considered as well-exposed:
As you can see, it strikes a pretty good balance between the two previously shown image samples – it’s not too dark and not too bright. There is also little detail lost, mostly in the windows as they reflect the most light. Given that’s just about how it actually looked like while standing in front of the building, you could say it is close to “real life” view. It could be ever so slightly darker or brighter, mind – generally, there is some wiggle room when deciding on the “correct” exposure.
It is important to note that you can’t actually capture a completely realistic image in terms of exposure. It’s not possible – even when using HDR technique (which distorts the image in other ways), although it can get you close if used well – because of the limited dynamic range of current imaging sensors. Our eyes don’t have such limitations to begin with – at a given time (under what you may call normal circumstances) we can distinguish both highlights and shadows in a particular scene much better than any camera. But then, that’s part of the charm and one of the things that make photography a creative process rather than a representation of reality.
All the Creative Choices
If all you wanted from this article is to distinguish underexposure from overexposure and understand the two terms, you can stop reading right about now. If, however, you are ready for my usual caveat, continue reading. Because none of the above actually matters, throw it out of your mind.
Back when I studied multimedia arts (I say it as if it was a long time ago!), I had this discussion with one of the more brilliant lecturers. We talked about whether photography, inherently, is representative of reality, of true events, true personalities, true… ambiance, if you will. In essence, whether or not photography is a lie. Now, this is a very complex subject, one we could immerse in very deeply indeed (an acquaintance of mine did her bachelor’s degree on the subject). But then, however interesting and thought-provoking, that would be a different article altogether. For now, with certain exceptions that involve a lot of deliberate effort from the author, I believe photography really is a lie and does not represent truth or reality, at least in the most straightforward way. Put another way, photography is always a creative process. Even if one is attempting to “show reality”, he has to take certain creative steps to achieve this.
You may be wondering what underexposure and overexposure have to do with this, and the answer is simple. Just like your choice of lens, camera, subject, angle, time, composition, light, settings, color or black and white, film or digital, exposure is a creative choice that you make to help achieve a particular goal. Which in turn means there is no correct exposure, and thus no over- and underexposure. All you have is the correct or incorrect exposure for you, for your goal, for your work.
The settings your camera would choose for you in any given situation are not the correct settings – merely a suggestion of settings that could be considered the most common, middle-of-the-ground choice. Of course, even if you want to overexpose or underexpose, often it is good to expose “properly” in camera so that you preserve as much details as possible and make your creative choice later in post-processing.
Creative choices are only such when you make them with thought, deliberately, and only when they pay off. So how do you expose a portrait of a woman photographed in front of a window frontally? Do you want to make it a silhouette or expose for the woman’s face and blow-out the background, effectively isolating her and removing the environment? It’s a choice.
And not just in such straightforward situations, either. Generally, I tend to expose my photographs slightly “to the left” – as in, “underexpose” them a little bit. From a purely technical standpoint of digital photography, that is a wrong choice, but I am not hung up on technical perfection to such an extent and prefer to do as much work as I can during the process of image capture and not post-processing. Why underexpose? It may have something to do with the fact I like darker environments, but more than anything else it helps me emphasize the subtlety of light. For me, photography is light even more so than a story or a person, and I like it subtle, I like it brushing my subjects slightly, barely touching them. And so I make my creative choice.
As you can see, the terms don’t really matter. Yes, they will help you communicate with your fellow photographers and not feel out of place among the more technical folk, but it does not help your creativity in any way. There is no underexposure and overexposure, there is only what you need, what you want to achieve.
Even though exposure is largely a matter of creative choice, there are still a couple of guidelines that might be useful. The first is that you should avoid overexposing any areas in the photo that you want to retain detail, since it is impossible to recover any details that have blown out to pure white. (Areas that look pure black can usually be recovered.) The second is that you have some flexibility to brighten or darken the photo in post-processing later, so it is not always a decision that you need to make in-camera.
If you’re interested in maximizing image quality and retaining as much detail as possible, however, it’s may still be okay to overexpose some areas. For example, consider this image:
In this portrait of an Eastern Screech Owl, I overexposed the sky a little bit so I could get more detail and less image noise in the shadows. But I made sure not to overexpose any of the feathers on the owl, or the pieces of bark on the tree, because it would be impossible to fix those in post-processing if they were overexposed.
For more information on optimal digital exposure, you can read our article on Exposing to the Right.
Exposure in your image is largely a matter of creative choice. Still, most of the time, you will want to expose in camera so that you can retain as much detail as possible in post-processing. After that, you can make minor modifications to your exposure to give an image a bit more of a dark mood with underexposure, or a more bright mood with overexposure.