“Light makes photography. Embrace light. Admire it. Love it. But above all, know light. Know it for all you are worth, and you will know the key to photography.”
– George Eastman, Inventor
Have you ever brought home a new TV, set it up, and turned it on, only to realize that the picture looks either incredibly dark or blazingly bright? But you’ve got this under control. No problem. You head to the image settings, find the contrast, brightness and saturation levels… only to find yourself with a headache an hour later, having tried every conceivable combination to no avail, and now too exhausted to watch your new purchase anyway.
Ok, so maybe that’s a bit hyperbolic. Yet, at the same time, trying to capture the perfectly balanced photograph can feel very similar, especially for novice or intermediate level photographers just beginning to venture into using the manual setting on their cameras. But if you’re struggling to achieve your desired results, just remember one thing: it’s all about light.
As we’ve discussed in two of our recent guides, “Understanding Aperture: Controlling Light Based on the Exposure Triangle” and “Mastering Shutter Speed to Capture and Freeze Motion,” there are three elements, all related to light, of which the exposure triangle is comprised: aperture, shutter speed and ISO. ISO plays its own specific role regarding exposure and light, and a seemingly simple role at that. Stated briefly, ISO serves to brighten (or darken) your image. For example, if you’re shooting at night or in a dark or dimly lit room or landscape (all situations where ISO is particularly useful) and your photo comes out without enough light exposure, just increase the ISO level and brighten it up. Easy, right?
Not so fast! As with aperture and shutter speed, using and adjusting ISO introduces a number of variables that affect how your image appears, and, while ISO can greatly benefit the quality of your photographs, not all of its effects are necessarily positive.
This guide will round out our trilogy by focusing on such issues, and on all things related to ISO, including how ISO interacts with the other two aspects of the exposure triangle. Specifically, we will address these questions:
What is ISO?
What are the pros and cons of using ISO?
What do variations in ISO levels look like?
What happens if increasing ISO is the only available option?
Let’s take a look at the world of ISO.
What Is ISO?
A good way to begin defining ISO is by understanding what the name itself means. ISO comes from the Greek ‘isos’, which means equal. While ISO refers to the International Organization of Standardization, the organization responsible for setting the standards for a digital camera’s sensitivity rating, it is not an acronym. Instead, the founders of the organization decided to give it the short form, ISO, so it is the same across all languages.
In reference to your camera, ISO is simply a measure of how sensitive your camera sensor is to light. While aperture and shutter speed are essentially physically mechanical functions – with aperture being determined by the size of the opening in your lens, and shutter speed being controlled by the timed opening and closing of a curtain-like shutter – ISO is more of a computerized function. All digital cameras contain computers, and one role of these computers is to translate the information gathered by your camera’s aperture and shutter speed. Once the information is obtained and stored, the camera’s computer can be used, via the ISO feature, to brighten a given image. In this sense, using ISO on your camera is much like using image-editing software on your personal computer or laptop.
ISO Values and Exposure
ISO values (or ISO settings) are measured in whole numbers. On most cameras, ISO values range from ISO 100 to ISO 6400 (although some high-tech lenses allow for values far beyond that), with ISO 100 considered to be a low setting and ISO 6400 a high setting. The following scale of standard ISO values with corresponding images will help you visualize part of this range:
As you can see, these numbers correspond to the level of brightness you are introducing via the ISO function. For example, an image at ISO 400 is twice as bright as that image at ISO 200.
We can see that the first image at ISO 100 is underexposed, making it difficult for us to make out the features of Darth Vader. Even at ISO 200, he still appears too dark for us to see any significant detail. However, by raising the ISO value to ISO 400 and brightening the image, we can begin to see more detail emerge.
As we see in the photos above, using ISO to adjust the brightness of an image can do wonders for your work. However, as we mentioned in the introduction, increasing your ISO values can work to the detriment of your images as well.
Basically, when you increase your ISO, you are lowering the quality of your image. In some cases, as with the images above, increasing your ISO setting will have little to no effect on the overall quality and clarity of your photos. However, in that series, the ISO levels were doubled on the lowest levels of the value scale, and therefore the incremental loss of quality was all but unnoticeable.
When dealing with much higher ISO values, the diminishment of image quality is far more apparent. Let’s take a closer look at a series of images using LEGO Darth Vader again to demonstrate what we mean:
It becomes clear while looking at these images at higher ISO values that a great deal of quality is being sacrificed as the ISO is increased. In the previous series, we were faced with an image that was noticeably underexposed, and, by doubling the setting twice on the low end of the value scale, we were able to increase the brightness without losing any quality. However, in the case of this series, what we see is an image becoming increasingly overexposed instead. The image becomes too bright to the point at which details are “washed out,” and the crispness of the image has decreased as well.
In the examples above, we’ve taken a quick glance at how higher and lower ISO settings can over- or underexpose an image. Again, the fundamental purpose of the ISO feature is to brighten or darken an image to achieve the most appropriate exposure, and therefore brightness is the most obvious effect using various ISO values. But, as mentioned briefly earlier on, there are other effects that come along with raising ISO levels, as well as different environmental and artistic circumstances under which you would want to use a high or low ISO setting. In the remainder of this guide we will:
Define and highlight the digital effects of using ISO
Determine when to use an increased ISO value and why
Determine when to use a low ISO value and why
Examine how ISO works alongside aperture and shutter speed
The Photographic Effects of Using ISO
One useful way to begin understanding the effects of using ISO – effects other than brightness levels – is to use an analogy related to capturing audio rather than images. Imagine that you’ve recorded an interview you conducted with someone by using a digital recorder with a built-in microphone. When you upload it to your computer, you realize that the sound isn’t loud enough to make out what’s being said. Of course you want to make the interview intelligible, so you use sound-editing software to increase the audio level.
However, as you increase the audio level incrementally, you realize that, while the voices captured in the interview are becoming much louder, other noises are increasing as well. Sounds that came from you moving around the microphone (signal or electrical noise) and sounds that came through the window like dogs barking, a car alarm going off, and traffic noise (ambient noise) are now audible, much to the detriment of the audio’s clarity. In other words, in this case, “louder” doesn’t mean “better”; rather, it means noisier.
Noise, Grain, Color and Dynamic Range
In the example above, the volume or loudness of the audio is analogous to the brightness of an image. And just as more signal and ambient noise are introduced when raising the volume of the audio, the exact same thing is true when raising the ISO value on your camera.
The reason that noise in audio recordings is so appropriate as an analogy is that “noise” is also the term used for the detrimental granular effects that raising your ISO has on your images. Signal noise in an image is known as “grain.” When you hear someone say that an image is “grainy,” it means that it lacks clarity and crispness due to an overabundance of noise. When you increase your ISO setting, what you’re really doing is increasing the electronic signal in your camera, which causes an increase in the sensitivity of your camera sensor to light. The more sensitive your camera’s signal, the more noise and grain is introduced into an image.
In addition to noise levels, color is also affected by increasing ISO values. This is because increasing the sensitivity of your camera sensor to light leads to digital pixels rendering the “true” color of an image improperly, causing discoloration. In cases where high ISO values are being used, the colors in an image often won’t “pop,” but rather appear muted and distorted.
The third drawback of using a high ISO setting is that it lowers your camera’s dynamic range. Dynamic range refers to how well your camera is able to capture fine detail in areas of both light and shadow within an image. When the dynamic range is lowered, a significant amount of a photo’s richness is depleted, sacrificing the visual intricacy of your image.
When to Use Higher ISO Settings
As we saw earlier, raising your ISO levels, particularly at lower settings, can help bring an underexposed image into a more proper exposure. Here are a couple examples to demonstrate the simple brightening of photos to exposure levels where more details can be appreciated and the richness of colors is restored:
In each photo set, the images are underexposed to the degree that we almost have to squint or peer at the photos in order to make out the details and colors. Simply by increasing the ISO value (by about 4x), each of these photos was brightened to a proper exposure level without sacrificing any significant image quality.
Brightening your images is clearly the most obvious and fundamental reason to increase your ISO, but there are also several environmental circumstances when raising your ISO setting is going to yield the best results. Two of the most common such instances are when you’re shooting at night (particularly for sky and star photography) and when you’re shooting indoor spaces where natural or electric light is insufficient. Let’s take a look at representative photos of both of these situations:
Setting ISO for Night Photography
Setting ISO for Low-Light Indoor Photography
In the first two examples, we have two different photos taken at night: one of a bridge and one of a starry sky. Images like these captured at night often come out far too dark due to the lack of natural light in the shooting environment; this can be seen in the first photo of each set. By raising the ISO in these situations, we can achieve better results that allow for more detail to be seen.
Likewise, the second two examples were clearly shot indoors with very little natural or electric light. Details are obscured, once again, due to insufficient light in the area where we’re shooting. By raising the ISO value in each case, we’re afforded a much clearer, well-exposed image.
The third instance in which raising your ISO level is beneficial is aesthetic or stylistic, rather than corrective. Introducing a certain level of grain into your images can have a positive aesthetic effect that can give your photos a certain “look” that might nicely suit the subject matter of the photo itself. Let’s take a look at a few examples of images that benefit from including some noise:
Here we have a beautiful photo of a row of antique books. This shot was taken with a higher level of noise in order to complement and enhance the natural coarseness of the books themselves, but also because such an effect mirrors the idea of “the antique” and matches the nostalgia for bygone eras.
Here we have another instance of an image with increased grain that nicely complements the subject of the photo. This old, weathered door, while coarsened naturally by time, is enhanced greatly in stylistic effect by adding some noise into the image by increasing the ISO. If this photo were taken on a lower ISO setting, it would appear more crisp and smooth, and while the door would still be an attractive subject, it would lose some of the “vintage” feel achieved by introducing grain into the image.
In this final example, we have a photo that was originally in color and converted into black and white. The reasoning behind this choice is that the photographer wanted to achieve the feel of an old Hollywood movie. However, the photo was also taken with a higher ISO, introducing grain into the photo to replicate the rougher film stock used in movies from the black and white era. In many cases, low levels of noise often give black and white images a pleasantly dynamic effect that otherwise might not be achieved, adding to the aesthetic value of a photograph. This is also a useful adjustment in instances where you absolutely cannot capture the type of image you want without employing a high ISO value.
When to Use Lower ISO Settings
As stated earlier, the most basic function of ISO is to brighten photos that are too dark and/or underexposed, often because they were taken in environments with insufficient light. However, when there is sufficient (or an abundance of) light, you will want to keep your ISO value as low as possible. If too high an ISO setting is used in such areas, you’ll often find yourself with an image or images that are overly bright, leaving you with washed out, overexposed photos.
While there are several reasons for using higher ISO levels, the main and most common reason to use lower ISO settings is simply that photos come out overexposed and “bleached.” In order to avoid this, if you’ve used too high of an ISO value, simply reverse the process exercised in the previous section and lower your ISO levels. Here are a couple instances where lowering your ISO is appropriate after having first taken photos that came out overexposed:
The images here were initially taken with higher ISO values which rendered them deficient in detail and clarity due to overexposure and using too sensitive an ISO setting for the amount of light in the shooting environment. By lowering your ISO, you regain your full range of detail.
You may also have noticed, particularly in the second example, that the color of the image was drastically altered to the detriment of the photo. This is another reason you want to keep your ISO low in many circumstances. Colors will appear paler and less defined due to the excessive brightness of the images if your ISO setting is set inappropriately high. This happens most clearly in images with bright colors, but in images of all types as well.
The last reason to use lower ISO settings is that the dynamic range is lowered, sometimes minimally, sometimes severely. Remember, dynamic range refers to how well your camera captures details in both the highlighted and shadowy areas of an image. In each of the examples in this section, particularly in the interior shot, you can see how details are often washed out. Especially vulnerable to this effect are the shadows between objects close to or layered upon each other, the hard edges around solid objects, and subjects or objects at a greater distance from the photographer.
Tip: Native ISO
One way to preserve the clarity and quality of your photos when using ISO is to shoot at your camera’s “native ISO.” The native ISO on most digital cameras is generally ISO 100 or ISO 200. How do you know what your camera’s native ISO is? Simple: Enter your camera model (brand name and number, etc.) into a Google search, along with the words “native ISO,” and the results should come up immediately. Knowing your camera’s native ISO will also give you a reference point when raising and lowering your ISO settings.
ISO, Aperture and Shutter Speed
Manipulating aperture and shutter speed can allow you to explore a vast range of aesthetic and stylistic variations in your work. Changing your aperture not only changes how much light is exposed to your camera sensor, but also the relative level of focus and depth of field in a given image. Shutter speed also affects light exposure by raising and lowering your camera’s shutter, but also functions as a tool for freezing an object in motion or allowing motion blur to appear. Below is a visual reminder of how this works:
Often times, photographers will refer to ISO as the “third aspect” of the exposure triangle, not in the sense that it’s less important to them than the other two, but rather that they determine their aperture and shutter speed settings before they make any adjustments in their ISO values. This approach allows you to select your more dynamic settings first in order to tell whether raising your ISO value is necessary or if you can leave your native ISO in place.
Let’s use some visual examples to demonstrate how ISO works organically with aperture and shutter speed:
This photo was taken with a low ISO value of 200, which seems distinctly low given that it seems to have been taken in low light as the sun was setting. However, it was also taken with a wide aperture setting of f/1.8, with the lens almost wide open to allow for an increased amount of light to enter in order to avoid poor exposure. Using the wider aperture setting also allowed for the photographer to use a faster shutter speed (which allows less light in) of 1/500 of a second in order to capture and freeze the subject in motion.
This image was taken with a little bit higher ISO (400) than the previous example, as, once again, it seems to have been taken as the sun was rising or falling, and therefore with less light. A faster shutter speed, 1/500 of a second, was used again in order to freeze any movement by the subject, even while this reduced the amount of light entering the camera. In addition, in this case, a mid-range aperture of f/5.6 was used in order to achieve a greater depth of field, which also allows less light to reach the camera’s sensor. In this way, by using a higher ISO the photographer was able to use shutter speed and aperture settings that allowed them to achieve the desired effect.
Lastly, this beautiful night photo was taken with a very slow shutter shutter speed of nearly 30 minutes, and a medium level aperture setting of f/4. The long shutter speed allows as much of the available light as possible (the light coming from the sunset and the stars) to enter the camera, and also to capture a movement effect in the stars due to the Earth’s rotation during the extended interval that the shutter was open. The medium aperture allows for the photographer to achieve a shallower depth of field, keeping the subject in the foreground in high focus while allowing for a dreamlike effect to be achieved in the background by allowing for less focus. But given the extreme lack of light in the shooting environment, the photographer used a significantly increased ISO value of 1600 in order to brighten up the image and achieve proper exposure.
Each of these examples represent perfectly balanced photos, with various ISO levels used for particular reasons so that the photographer could achieve their desired effects.
Tip: Using ISO Wisely
It’s important to keep in mind that while you always want to capture the cleanest, sharpest image you can, this is no reason to shoot with a low ISO in every situation simply because a higher ISO value increases image noise. In fact, an image with a minimal degree of noise is almost always of a higher quality and preferable to an image with unwanted motion blur or unbalanced focus. In other words, when in doubt, err on the side of setting your aperture and shutter speed appropriately, even at the expense of introducing a slight level of grain.
As we hope you’ve learned, ISO is nothing to be automatically avoided, let alone feared; it’s just one more tool in your image-maker’s toolkit and a highly useful one at that. Not only can using ISO bail you out of many a photographic jam, exploring different combinations of ISO can also be every bit as enjoyable as experimenting with aperture and shutter speed.
Always remember: playing with light is fun, and tinkering with your camera’s manual settings is, too. Using ISO is just one more way for you to enjoy the process of developing your own taste and artistic style while you learn.
We hope that you’ve enjoyed this third and final guide rounding out our series on the three aspects of the exposure triangle. We also hope that you’ll keep these guides close by and accessible as you continue to experiment with manual photography. You never know when you might need a quick refresher on how aperture, shutter speed, and ISO work together organically to create stylish, high-quality images.
Seth is the CEO of PHLEARN and an avid writer, photographer, startup investor, and business mentor in Chicago. He joined PHLEARN in 2016 and has been focused on expanding the community to reach millions of new Phans and make learning fun for the next generation of great artists.
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