Balancing the Three Parameters of Your Camera - Aperture, Shutter Speed, and Focal Length
I find the technology of cameras fascinating. Their ability to observe a 3-dimensional scene and translate it into a 2-dimensional space feels like magic. Every year, they get better, smaller, lighter, faster, sharper, etc. However, despite camera advancements, they continue to function in much the same way. The technology within all cameras operate these three primary setting:
Dilation of the “iris” of the camera’s lens
Lengthening (or shortening) the amount of time a shutter stays open
Altering the field of view while compressing elements of the image*
No camera can escape the balancing act of these three since each one deals with a different aspect of image capturing. Whether you’re filming or photographing, understanding how a camera’s technology works to alter these parameters will help make you a better visual storyteller.
*keep reading if you believe I missed ISO or light sensitivity
Gathering Light
While you do not need a biology degree in order to get any of this, having a basic understanding of how the eye sees its surroundings will certainly help. The human eye is still a complete marvel of design and function. Nothing can replicate it, and no one can really explain its development. Even Darwin himself admitted the design of the eye baffled him.
Put simply, your ability to see is based entirely on your eye’s ability to absorb light rays that bounce off objects and are then translated, by your brain, into an image all within nanoseconds.
Light rays are separated into different frequencies which are picked up by the different cones in your eye resulting in you experiencing colors. Alternatively, the rods in your eye help you see in low light but have no ability to distinguish colors. Pupils opens and closes depending on how much light there is. When it’s darker, they open wider (dilate), and when it’s brighter, they close tighter (constrict). In summary, the pupils allow light to pass through to your rods and cones which send signals to your brain resulting in vision.
The camera is the eyeball!
If you think of the camera as an eye, everything I’ve written above makes more sense… hopefully.
Think of the camera’s sensor, or the film within the camera, as those rods and cones that are gathering light so the processor, the camera’s brain, can translate it into an image. Within the lens contains an aperture that acts exactly like the pupil allowing more (or less) light inside the camera’s body. What gives us that still image is a shutter that for a specified amount of time opens and then closes preventing any unwanted light from getting inside the camera. Bam! Analogy justified.
The ISO Myth
Since you’re most likely screaming at your computer (or phone) that I’ve totally forgotten one of the major settings on your camera, let’s address some ISO misconceptions before we go any further.
Physical “analog” film rolls have different ISO numbers when you purchase them. In this case, ISO is referring to chemicals in the film that result in light sensitivity. The higher the number, the more sensitive it is to capturing light. There is no way to change this in camera once the film is loaded. However, ISO is a setting on digital cameras. Because of this, many believe ISO, as a setting that you can change, affects the digital sensor’s sensitivity to light.
This is just not true.
A digital camera sensor has something called a native ISO where it gathers light information at its best and cleanest. As ISO is increased or decreased, your camera begins boosting or reducing the image’s brightness which introduces “noise” into the photo. You’ll know exactly what I’m talking about if you’ve ever increased an underexposed photo’s brightness in your computer while editing. The image starts to look pixelated the more you push it. This is why photographers try to shoot closest to a camera’s native ISO as possible.
A few expensive cameras have what’s called a dual-native ISO, so there are two places where the camera is able to capture an image without boosting or reducing the exposure. I’m going to send you to THIS VIDEO if you’re interested in diving into it deeply. If you don’t care, just know that it exists to give you two brightness levels where your camera looks sharpest. Check your manual to see where your camera’s ISO is best.
Focal Length: Field of view
This is determined by the lens on your camera and is indicated by the little “mm” on the lens’s spec sheet. The lower the number, the wider the field of view, so if you’re trying to capture a lot in a scene, you might reach for something like 16mm. Whereas, if you’re trying to isolate a small portion of the image, you’ll probably grab something like a 100mm or more. This is often referred to as the “zoom” of a lens. However, unlike a digital zoom that just crops into an image electronically, the optical elements actually physically move, shifting the light’s convergence point in the lens and changing the field of view of the image.
What this also results in is a difference in how elements are compressed in your image. A wide angle lens (smaller “mm” number) spreads out the elements of a scene and grows the foreground of the image. A long lens (larger “mm” number” compresses a scene growing the background elements of the image.
Shutter Speed: Length of Time
The length of time at which the sensor is exposed to light is called the “shutter speed.” A slow shutter speed stays open for a long time while a fast shutter speed only opens for short amount of time. As you can imagine, your scene will have to be brighter for a faster shutter speed in order for the sensor to have enough time to absorb the light. Slowing down the shutter speed while subjects are moving results in more motion blur, which is how we get super smooth images of water. My current camera is capable of taking a photo at 1/4000 of a second using its mechanical shutter. That’s fast!
Aperture: Depth of Field
The lens’s aperture is a mechanism that, like an eye’s pupil, dilates and constricts to let more or less light pass through the shutter and into the camera body where the sensor is housed. The aperture has two major effects on a photo. Firstly, it will allow more or less light into the camera so we can successfully capture images during darker or lighter situations. Also, the change in aperture size creates what is called “depth of field.” When you have a shallow depth of field from a very open aperture, it means less of your image is in focus. Conversely, when you constrict that aperture to a very narrow hole, more of the image will be in focus resulting in a wider depth of field.
The balancing act
I call it a balancing act since shifting each parameter in different directions results in completely different images even of the same subject. Failure to balance them will cause you to either under-expose (make too dark) or over-expose (make too bright) your photo. Learn to properly expose an image before you experiment so you understand how to balance all the camera settings. In most cases, you will be adjusting aperture and shutter speed most of all especially once you’ve got your composition and framing determined.
As a quick example, any time I arrive on a scene to photograph a subject, I will decide on my focal length first. This will determine the overall look of my composition. Once I’m satisfied with my field of view, I decide which of the other parameters to prioritize (aperture or shutter speed). If a shallow depth of field is important to the composition, I set aperture first. If I need a slow shutter speed for long-exposure photography, that’s the setting I mess with. After my prioritized parameter is where it needs to be, I check lighter areas and darker areas to adjust the other parameter and achieve perfect exposure. If you’re wondering how I handle ISO, I set it as low as possible on a digital camera to keep the image as sharp as possible. When I’m using film, ISO is already determined by the film type, so I just adjust everything else accordingly.
If you’re struggling with balancing aperture or shutter speed, set your camera to either Aperture Priority or Time/Speed Priority and focus on how the camera automatically adjusts the other. Most modern digital cameras have an ability to do this, and it can really help you wrap your head around how aperture or shutter speed effect the scene.
Final Thoughts
Once you’ve got it down, and you can properly expose an image, it’s time to start experimenting. Try long-exposure photography first. Go to a river or waterfall and set the shutter speed to a few seconds long and see where you have to set your aperture to get a good exposure. Try photographing with a very narrow aperture to get a lot of the photo in focus and see how long your shutter speed is compare to photographing with a very wide aperture. Use a zoom lens or purchase a couple prime lenses and photograph the same subject at different focal lengths to see how it changes the overall composition.
Experimenting with your camera settings will help you grow as a photographer. It is through trial and error that you will learn to achieve the composition that is in your mind and discover your artistic style. Be ok taking “bad” photos in order to get to the “good” ones. I cannot express how much making photography “mistakes” over the years has helped me. You’ll likely take hundreds (maybe thousands) of “bad” photos before you start getting actual portfolio pieces. With each photo you take, you will learn how to better balance the parameters of photography.
-Jude