The Exposure Triangle

Start to juggle three balls - what could possibly go wrong?
I don't know how you felt about it, or do feel about it, but that's how I experienced the thought of shooting fully manual for the first time. In fairness, it wasn't as if I purchased my first DSLR and started shooting manual straight away. It was a progression. I started on fully automatic, learning what the camera thought was ideal exposure, then onto shutter and aperture priority modes and eventually onto fully manual. 

The three balls were replaced with ISO, Aperture and Shutter Speed. But I knew that if I could learn to juggle those three things, I would have much more control of my camera and achieve the images that I saw in my head, the way I thought they should look. Today's cameras are very good at getting exposure right but don't possess any artistic flair.
While the exposure triangle determines perfect exposure, it's not rigid. We have to learn what proportions of each component to use in each scenario so that we achieve the desired result. Do we need to compensate for lack of light? Do we want to freeze the action or give some perceived sense of motion to the image? Do we want to add some background blur to the image (bokeh) to isolate the subject or for artistic effect?

Shooting manual isn't rocket science, but it does take an effort to learn and having learned those principles it needs to be practiced. Nothing worth having comes easy, and these skills are well worth having. It makes photography more satisfying as an art form and takes your images from"Oh that's nice" to "Wow, who took that."

So does that mean we should be shooting fully manual at all times and in all circumstances? Absolutely not. The aim of learning this isn't to drop all other options, but to know how to adapt to any given situation and take back control where necessary. 

In another blog, I have gone deeper into the meaning of each element but let's be clear here what we are considering. 

ISO is the sensitivity to light of the sensor that catches the data that makes up the image. Its the same principle as film but the main difference is that we can choose the ISO for each image. Back in the day, we had to choose the sensitivity of the film that we loaded into the camera and were stuck with that until we had finished shooting that roll. The lower the number, the smoother the image will be but requires the most light to be available to make it workable It's less sensitive to light). Shooting high numbers allows' us to work with less available light (It's more sensitive to light), but there could be a trade-off with noise being introduced in the image. There are ways of fooling the sensor, but we'll cover that in the blog about filters. Today's cameras are so sophisticated that noise is less apparent than it once was, and in some cases, noise is attractive if used in the right way.

Aperture means opening and is measured in "F" numbers. Bizarrely the lower the number, the larger the opening. So the opening is wider at F2.8 than it is at F8 which in turn is open wider than at F22 etc. The F-stop also regulates the depth of field captured in the image. F2.8 is a narrow depth of field. As an example, you may want to take a portrait where the person is in focus, but the background is thrown out of focus, a low f-stop number would be the preferred choice. F22 gives a large depth of field. You may want to use this on a landscape where you require the scene to be in focus from the objects in the foreground right to the far distance.

Shutter speed is exactly what it says on the tin. It's how long the shutter is open, exposing the sensor to light. The longer its open, the more light gets to the sensor. It also controls movement. A fast shutter speed will freeze motion, and a slow shutter speed will give the image a sense of motion.

So how do we start making our choices? Before we go there, we should consider some math. There isn't an actual number that represents perfect exposure but just to give a sense of proportion, I will use the number 99 as perfect exposure. We can't use more than that number, and we can't use any less. If we do, we will be overexposed or underexposed the image.
If we made ISO 33, shutter speed 33 and aperture 33, we would have perfect exposure. In a similar fashion, if we made ISO 10, shutter speed 29 and aperture 60 we would have perfect exposure. In any combination, if we have a sum total of 99 we have perfect exposure.

So let's start making some decisions. Our first step is to decide on whats important. I'm not talking about subject or composition; I'm assuming that's already decided. We need to rotate the triangle. Obviously, we start with the most important aspect of the image. Our second most important area then compliments it, and the least important area fills in the gaps

Some examples:-

I am at my son's school soccer game. It's a bright sunny day, and the game is fast moving. I want to include a number of players in the shot. My priority has to be the depth of field so that players at different distances away from me are all in focus; I choose my aperture. I don't mind a little motion but want to freeze the image if I can so I then choose my shutter speed, and then I fill in the gaps by selecting my ISO.

I'm standing at a wonderful viewpoint, the clouds are perfectly complimenting the hills in the distance but the light is fading fast, and the valley floor will soon be in shadow. I have to prioritize the ISO because I know the sensor will need to be sensitive. I want the whole image in focus, so I next chose my aperture, and then the shutter speed fills in the gaps.

So are these hard and fast rules for these scenarios? Absolutely not, they are just plucked out of the air as examples of how we should think about the exposure triangle. Every time you stand behind the camera, there will be choices that need to be made. How you make those choices will become "your style," and the more experience you get in making them, the more consistent your photography will become.

So how do you get that experience? The short answer is practice, but there is good and bad practice. Bad practice would be to go out and take random photographs without a set routine. You'll get bored and go back to shooting automatic; I can almost guarantee that. Or you can adopt a proactive approach to learning. Is not perfect but this is what I realized and what I did about it. I realized that I needed to know my camera inside and out and I needed to know what was successful and what wasn't. I also had to have a set purpose when I set out, so it wouldn't become mundane. I would set out with the aim of taking photographs that represented the alphabet. That meant that I would need 26 photographs. No more than that because I wanted each to be taken with care. One photograph with the subject starting with a different letter of the alphabet. An apple, a ball, a cat and so on. Because there was a variety of subjects, I needed to make decisions on each. A cat, should I freeze the action of it running across the garden. A flower, should I isolate an individual bloom. Each gave me the opportunity to practice the exposure triangle. Each gave me the opportunity to get to know the buttons, knobs, and dials of my camera and as an added bonus, each gave me the opportunity to practice composition. It was a win win win situation.

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