The Exposure Triangle: Master Aperture, Shutter Speed, and ISO for Great Photography

photography-exposure-triangle

Aperture, shutter speed, ISO...you have probably heard these three terms before, but maybe struggle to understand how they interact with each other. After all, when shooting in manual camera mode (and you should learn to do this!), you will need to set each of these just right to capture good looking images. 

The exposure triangle is a basic visual representation of these three elements, and helps to teach you how they work together so you can score those great images yourself! 

The exposure triangle is one of the most critical pieces of the photography puzzle to get right. 

Before we dive deeply into this topic, it is critical to keep in mind that photography is a balancing act. Every time you make an adjustment to one of the three elements in the exposure triangle, you are impacting your photo output. While more experienced photographers might have a great ability to jump right to settings that are in the ballpark, it often will take a few test shots to dial in the settings just right - so don't feel bad if you are taking some time to adapt your settings, it is something that is learned with practice!

The Exposure Triangle

Aperture

Photo taken with a Canon 135mm f/2 lens on a 5D Mark III - you can see the significant amount of bokeh blur, and how the couple is nicely separated from the background

If ever there was a time for us to be photography nerds, this would be it.

Aperture is one of our favorite aspects of the exposure triangle - namely because of how it impacts the resulting bokeh effect (the blurred out fractal backgrounds you see in many images). Because aperture influences the depth of field, choosing a lower f-stop will produce a wide aperture, which produces this effect, and separation of the subject from the background. This is perfect for portrait photography, and is one of the defining elements that draw people to photography of this type in many instances - even though they might not even realize it.

Now, let's slow it down for a second, as we know there were just a few terms thrown out that you might not fully comprehend. The aperture itself is a measure of how open or closed the lens' iris is. The more open, the more light gets in. The more closed, the less light. Your camera is really an artificial eye!

The f-stop (or focal stop) is a measurement of focal length to the diameter of the entrance pupil. Lower f-stops produces a wide aperture, and the opposite is true, higher f-stop numbers produce more narrow apertures. When purchasing camera lenses, it is important to pay attention to the f-stop numbers and make sure they coincide with the style of photography you are looking to shoot. As we do a lot of portraits during engagement sessions and weddings (bride + groom, family, etc.), we have several prime Canon lenses that go down as low as f/1.2 - which provides us a lot of room for choosing an f-stop that will produce the beautiful bokeh effect we mentioned before.

Aperture is really one of the most powerful tools on your camera that has the ability to significantly impact your compositions, isolate your subject within a scene, and help create a photo that is distinct from much amateur photography.

Shutter Speed

Combined with flash, intentionally using a lower shutter speed (or your camera's bulb mode) will allow you to add some light dragging flare to your reception dancing photos!

While aperture is critical and pretty to think about, shutter speed provides more practicality to our photography. Shutter speed is the measure of how long the shutter (think: eyelid) stays open, effecting how long the camera sensor is exposed to light. Faster shutter speeds (higher numbers) give less time to collect light, and slower shutter speeds provide more time. The trade off is that, in general, higher shutter speed photos will be under-exposed (darker), but be able to capture more movement without blur or out-of-focus images; and lower shutter speed photos will be more over-exposed (lighter), but require less movement from your subject(s).

As might be obvious, choosing your shutter speed will be heavily dependent on your photography situation. Photographing dancing at a reception? A higher shutter speed will be better to help capture that movement without having blurry subjects. How about a bridal portrait? A lower shutter speed should be more than sufficient. The general rule of thumb we follow is to have your shutter speed at least 2x that of the focal length of your lens to minimize impact from camera shake - so with a 50mm lens, you would want to have at least a shutter speed of 100. In general, we use even higher starting shutter speeds for most images we take, because we tend to move quickly to capture candid moments during most weddings and sessions.

While these are the general guidelines of shutter speed, photography as an art allows the rules to be broken all the time. For example, with reception dancing photos, we often lower the shutter speed intentionally - even at the expense of some motion blur - in order to produce that feeling of actual movement in the image. While we wouldn't want to do this with every dancing image, it helps add some more flair, and lower shutter speeds can be used to light drag - making even more interesting effects!

In the dancing scenario, it is especially easy to experiment with shutter speeds as often reception dancing will go on for hours at a time, allowing more space to comfortably experiment. In addition to manually lowering the shutter speed, you can also put your camera into bulb mode, where you hold the shutter button and the shutter stays closed until you release. This can make for some exceptionally interesting photos, and is especially valuable if you are trying your hand at astrophotography, too!

ISO

Because of the low light scenario of shooting in a covered valley area at Forbidden Drive (in Philadelphia's Fairmont Park), it was necessary to bump our ISO to 600 for this image. With a Canon 5D Mark III and some grain removal in Lightroom, the higher ISO had no noticeably negative impact on the image quality and still allowed us to shoot with the natural light that was present.

ISO is the most "artificial" of the mechanisms in place on your camera that are a part of the exposure triangle. While the aperture (the eye) and shutter speed (eyelid) might be easy to compare to natural parts of our bodies, ISO is much like a contact lens or a pair of glasses placed on top.

ISO is a measure of your cameras sensitivity to light and dark. The preferred ISO is 100, the lowest setting, which allows for the most crisp photographs to be taken. Of course, while ISO 100 might be easy to utilize in ideal lighting situations (outside on a lightly cloudy day in the morning or late afternoon), there just simply won't be enough light in other environments to get a good exposure. Even on a nice day, a step into the shade might require you to bump the ISO higher to increase the light in the image. The trade off, and it is significant, is a level of noise to be found in your image.

Now, there are instances where higher ISO's may be wanted. Creatively speaking, some people like the look of images with noise - it adds a grainy overlay that can look just fine in low doses. For astrophotography, higher ISOs are commonplace. In some cases, there may not be another option available (IE: no other lighting source available to utilize whether ambient, on camera/off camera flash).

Why would you want to use a higher ISO? When photographing in low light, there will come a point where you are already shooting at the widest aperture (remember: low f-stop number) and slowest shutter speed possible - which would typically result in the lightest image possible based on just these two - and ISO can be used to increase the exposure.

BUT HOW DO THEY WORK TOGETHER?

It's easy enough to understand each element of the exposure triangle on its own. They are not super complicated subjects to grasp, even if you aren't the most technically inclined person. However, it can become a challenge when trying to understand how they work together, and what the best settings for each would be in different photographing environments.

No doubt, it takes a lot of practice and constant attention to better understand how to get these settings just right. Every time we shoot a wedding or engagement session, and are faced with a new environment with it's own unique challenges, we are forced to figure out these settings on the fly. Fortunately, as we continue to develop our skills, it becomes easier to see the light and make sense of the settings.

The most important thing to understand is that - with every change of one variable, it will potentially require a change in another. If you increase the f-stop, it will make the resulting exposure darker, thus leading you to want to change the shutter speed to be a little lower (or bring the ISO up a stop if you don't want to sacrifice movement in your image).

The good news about digital photography, especially when shooting in RAW file format, is that you will be able to make some adjustments in post-processing in Lightroom (or a similar software). As we discuss on occasion in our blog, we often under-expose images intentionally - because we tend to like the look more (it lends more moodiness to the images), and because we find it often leads to our cameras capturing more raw data in the shadows of an image that we can then play with when editing the images.

The Exposure Hexagon - additional variables that impact exposure

In thinking about The Exposure Triangle over time, as we've studied and used the information that has been relayed time and again by other photographers out there, we started to come to the realization that dialing in the right exposure is actually dependent on more variables than just the three commonly discussed. Aperture, shutter speed, and ISO are very important - but are only representative of the choices you have to make on your camera body. However, it goes without saying, there are other elements at play that will dictate how your image turns out, and will impact your choice of settings of the big three.

In this following section, we discuss two additional variables that turn the triangle of old into...The Exposure Hexagon...We know it doesn't sound as pretty (hexagon? really??), but it'll do :)

Focal Length

Taken with a Canon 135mm lens, you can see the effect of a wide aperture on the image, with a lot of blurred background elements while the couple remains in nice focus. The longer focal length lens helps intensify this look, as even comparable settings with a 50mm would not have the same impact.

We found that someone did a write up about what they were calling...The Exposure Square...and their blog post made the case for focal length being just as important as the big three (aperture, shutter speed, ISO). This is a cool perspective, because focal length is a conscious decision made by the photographer, and directly will impact the outputted photos.

So, what is focal length? Unlike the main three variables, which are all effected by impacting settings on your camera body, focal length is describing your choice of lens. A 50mm lens is comparable to the human eye. Any lens that is longer (like our 70-200mm) has a substantially different effect, as does anything wider (like our 24mm).

We have already discussed how choice of f-stop can impact the depth of field (and resulting bokeh effect), but the choice of focal length will also impact this, too!

Longer focal length lenses naturally produce more of this beautiful compression, and it becomes less and less visible as your lens choice becomes wider. This is why you will generally find that portrait photography utilizes lenses with focal lengths of 50mm and longer, and landscape photography - usually with a desire for clarity and crispness of the whole scene, as well as an ability to capture more of the scene, will utilize wider focal lengths.

In addition to the depth of field impact, longer focal length lenses (like the 70-200mm) are also more prone to leading to some blur as a result of camera shake. You might think, this seems to be another way to negatively impact an image in a way similar to using too low of a shutter speed. And you're right!

Adding to the math requirements of professional photo taking is another rule of thumb: to reduce the impact of camera shake, you should use the shutter speed equal or higher to the number of your focal length. Examples: If focal length is 100mm, use 1/100th shutter speed or higher. If focal length is 50mm, use 1/50th shutter speed or higher. Like we said earlier in this article, we like to at least double this ourselves so as to have even less likelihood of impact on our images.

Of course, choosing a lens with image stabilization is one way to help counteract this and use lower shutter speeds if needed as well. The Canon EF 70-200mm f/2.8 II lens is really an excellent choice for both quality and the built in image stabilizer.

Light

Taken at Vestrahorn in Iceland with a Canon 5D Mark IV and Canon f/1.2 50mm lens, this image showcases landscape photography featuring a high f-stop (to get more of the picture in focus). Like most things in photography, the light from this day was pretty ideal for taking photos without any unnecessary filters - be it flash or even neutral density filters to cut down on some harsh sunlight.

While every photographer knows that light is a critical piece of the puzzle, framing it as something to keep in mind in conjunction with aperture, shutter speed, ISO, and focal length is something essential for grabbing the best photographs possible.

While in some ways, no doubt, we are talking about natural light from the sun, and ambient light from the environment - both of which greatly impact our photographs - we are also considering the use of flash.

Related: What is the Best Time of Day for Photography?

One thing all of the elements of exposure we have discussed already have in common is that they are all controllable by the mechanics of photography - ie: the things we purchase to take photos with like camera bodies and lenses. This is fundamentally why flash photography suits this model of The Exposure Hexagon.

Producing good quality images by utilizing all of your knowledge of in camera exposures, and getting the right lenses and knowing how to use, can only go so far for most people. As soon as you are placed in a low light environment, and if you still desire crisp and clear images, it becomes necessary to introduce artificial light into the environment. The challenge for many photographers is finding the way to make flash photography look natural, appealing, and flattering.

With flash photography, there are a number of significant variables that will impact the amount of light reaching your camera sensor - and the type of light. Changes in the shutter speed impact the amount of ambient light that can get in. Changes in the aperture directly impacts the amount of flash that will reach the sensor, and the amount of flash light available will be impacted by the flash power. Changes in the ISO provide changes to both the amount of flash and amount of ambient light reaching the sensor.

Fully manual photography, with a manual flash set-up (whether it be just an on-camera flash, an off-camera flash - or multiple off camera flashes, or a mix of the two), is really where photography becomes very complex. This play with light is where photographers can really distinguish themselves from others, and create their own styles. This ability to take a technical component of the photography process, and develop it into an enhanced art form, is ultimately why this play with light is so critical and a part of our photography process.

When it comes to flashes, we find the new Profoto A1 to be invaluable in terms of light and build quality, and ease of use.

LAST THOUGHTS

The many variables that go into taking a good quality, and good looking, picture can seem daunting - but also make photography into a life-long journey instead of something that can entirely be understood on the first day. It requires constant practice and experimentation. Even if you master photography in one environment, a new location or subject can create a new challenge quickly. As you continue to learn and take to heart the technical aspects of photography, you will find each challenge that approaches you to be a little bit easier as you pull on your wealth of knowledge more and more.

The exposure triangle is fundamentally a representation of the hard science behind operating a camera. "Back in the day" with film cameras, it was even more important to dial these settings in just right, but even now as professional photographers with digital cameras - it should always be a goal to get the right combination of aperture, shutter speed, and ISO to get the desired exposure in camera whenever possible. In addition to knowing how to set the main exposure elements, it's critical to keep in mind other elements at play too - as discussed here - the focal length of the lenses you choose, and the light that surrounds you or you bring to the image artificially by using flash.

We hope this detailed article has been useful for you. If you have any questions about getting the right exposure, leave a comment below!