So You Just Bought A Camera, Part One: Exposure

Wordiness level: 7 / 10
Time Commitment: Two cups of tea and four biscuits

Okay, you just bought a proper camera! Or maybe you inherited one. Or you robbed a camera store (hopefully not that). It’s tremendously exciting. New gear, new creative doors opening for you, and your cat just can’t wait to be photographed.

And then the learning curve hits.

Dear lord.

Not only do you have to grasp the basic technical controls of the camera, but you don’t know what they even mean! The top dial changes aperture, okay. But what is that exactly? And why is it measured in weird sequential numbers with an ‘f’ in front? Does exposure mean getting on a magazine cover? Why are all my pictures of my dog blurry? Is the UK bigger than Great Britain or is it the other way around?

It’s a lot to grapple with.

In this series, I’m going to break down the common stumbling blocks and make them easier to absorb and put to use. We’ll look at actual examples as well as talking about the principles behind everything, and knowing me there’ll likely be a silly analogy or twenty. We won’t talk about the controls of your camera much - the manual does that for you - but more so what they actually do.

Ready?

Part One: Exposure

The basic building block of understanding everything else. Here’s a little point by point of this post:

1. What is exposure, basically?

2. (a) What is correct exposure?
   (b) a stroll through Dynamic Range

3. What changes exposure?

4. The ‘exposure triangle’.

To illustrate a theme we’ll be hitting over and over: exposure is a creative choice, not an absolute. This might seem too dark to some, but it’s exactly what I wanted it to be.

1. What is exposure, basically?

Technically: it’s how much light reaches the film, or nowadays the sensor, of your camera. The more light hits your sensor, the brighter the image. You can get more light by exposing the sensor for more time, or by opening up your lens so that more light gets through.

Creatively: it’s the most powerful single variable affecting what your final image will look like, and how it will affect those who see it. It can make shadows clear and detailed or thick and black. It can make skies blown out into white or deep with blues and orange. It changes skin tone and even the subject of your image.

2.(a) What is correct exposure?

This is the first concept to grasp tightly: there is no correct exposure!

Think of it like this: you’ve just moved into your new house, and you want to paint some of the boring off-white walls. But which colour? There’s probably 100,000 internet articles about colour theory, correct selection of walls, which tones to avoid, etc etc. You can use that to guide you if you like… or you can just choose to paint every wall a horrifying orange, if that makes you happy! It’s entirely up to you and your creative vision.

Photography is the same.

Look at this image:

I’ve chosen here to keep Jeff’s suit and most of the door frame dark enough that it’s almost black. I know why I did it - the black border forms a nice frame and matches Jeff which contrasts him sharply with the background - but what’s important is that I like it! It’s more my style than the airy, white-out wedding shots that are probably a bit more common.

“Exposure is a creative choice, not an absolute rule.”

2.(b) a stroll through Dynamic Range

Okay. If you’re with me so far, you’re doing well. This is abstract stuff and requires a bit of mind-bending at first, so stick with it.

Dynamic range, despite sounding like a line of premium stove-tops, is a very important thing to grasp about camera exposure. Think about if you get out of bed to use the bathroom, switch the light on, then go back into a dark bedroom to avoid waking your spouse. You can’t see a thing, right? Your eyes are still adjusted to the bright bathroom. This is why you have to wait a minute while you readjust to the darkness and you can walk around without smacking your leg on the bedpost.

This is the key part: you don’t have the visual range to see in both the dark and the light at the same time.

Read that several times until it clicks, because it’s super important. Visual range is another way of saying dynamic range, it’s just that dynamic range is the standard photography terminology. (it’s actually slightly different, but it doesn’t really matter for this post)

Let’s use this picture from a camping trip Tina and I took earlier this year:

Look at that mist! Hot damn.

Anyway, this is a great example of dynamic range and how it works with exposure. You can see details on the stones, in the leaves of the trees, and a little on the bridge - this is because I ‘exposed for the leaves and the stones’, in photography jargon. I changed how much light I was letting in to my camera sensor until the image looked the way I wanted.

Notice also where there is no detail. The sides of the bridge are lost in shadow, and have just become featureless black. There’s also a patch of pure bright white in the center of the bridge, where the light is too much for me to expose both for that area and the leaves above. If I’d let in less light to get that detail on the bridge, the leaves would have been too dark for what I wanted. If I’d let in more light so we could see the side of the bridge, much more of the walkway and the sky would have been lost to pure white. I tweaked my exposure to get what I wanted.

“Everything in photography is a compromise.”

3. What changes exposure?

Okay, now we’re emerging from the forest of abstract brain-fumbling and into the bright lights of practical application.

We have three things that affect exposure. Two are mechanical, and one is electrical. Let’s deal with the electrical one first because it’s the simplest: ISO.

ISO just stands for International Standards Organisation - it’s a hangover from the film days. Modern DSLR or mirrorless cameras don’t have film, so ISO just refers to how sensitive the camera sensor is to incoming light. It’s not changing the signal - it’s just boosting the signal, like turning up the volume on your stereo. And, just like turning up the volume, the further you push your ISO the more distortion, or noise, appears in your image. It’s another compromise. The higher your ISO, the brighter your image, but the more speckly noise you introduce.

So far, so easy. Let’s look at the two mechanical variables.

First up, shutter speed. Let’s do a little practical analogy for this. Close your eyes (after reading this!). Open them for the briefest fraction of a second that you can, then immediately close them again. That’s a high shutter speed. Next, open them for a second or two, then close them. That’s a fairly long, or slow, shutter speed. The longer the ‘eye’ of your camera is open, the more light gets in. Fast speeds - a rapid eyeblink - freeze motion, like falling water droplets or birds in flight. Slower speeds introduce motion blur if you or your subject is moving.

Lightning! I set up my camera on the car roof for this (probably not the safest option…) and took a series of four second exposures, giving me time to catch the split-second lightning strikes. As they’re just massive bolts of electricity, there’s no real motion to blur.

The final variable of the trio and second of the mechanical two is your lens aperture. This is the trickiest one to grasp and has a lot of different things that go along with it, so we’ll save most of that for the blog post on aperture. Briefly, it’s the changeable opening in your lens that looks like this:

It can open up and close to let in more or less light. Think about a tap, or a faucet. When you turn the handle and open up the faucet, water (light) comes through. The more you open it the more water you get, and the more you close it the less water you get.

4. The ‘exposure triangle’

Okay, this is the last segment! If you made it this far, and you grasped all that, this bit will be relatively easy. Honest.

Let’s go full analogy-mode first. To start with, picture a room with three windows with venetian blinds, each on a different wall. If all three are closed, the room is dark. Now let’s say we open the blinds of one window. The room gets a little light! Awesome. We like it this way. Now, if we open up a second window, the room gets a little too bright - so we have to close the first window’s blinds to the exact amount that we opened the second in order to get back the light we had before.

Make sense? Make sure it does before you move on.

Now think about a room with a ceiling light on a dimmer switch. There’s a window with venetian blinds on your left, and another window with a thick curtain across it on your right. The ceiling light is our ISO, our electrical exposure variable. Changing it doesn’t let in any more light from outside, it just boosts the electrical signal to make things brighter. The venetian blinds are our shutters, or shutter speed, and the curtain is our lens aperture.

Changing any of these three will affect the light in the room.

Any time you change shutter speed, aperture, or ISO, you make your image brighter or darker. If you want to change one for a different reason - say, you need a faster shutter speed to capture your hyperactive five year old - then you need to compensate for that change by changing one of the other two. If you don’t, your image will be too bright, or too dark.

Let’s go back to the room just to nail this down. You’ve got your electric light, your venetian blinds, and your thick curtain. The light is at half-power, and the blinds and curtain are both open halfway. Say you want to switch the electric light off - maybe your last bill was a bit high! - so you’ve lost a half of one of your light variables. To compensate and keep the room as bright as it was, you can open the curtain all the way, or you can open the blinds all the way, or you can open each of those a quarter of the way. The point is that a change in one must be counter-balanced by a change in one or both of the others, unless you want to make the room/image brighter or darker.

There’s just one final thing to cover: changes in light are measured in stops, which mark out a halving or doubling of the light. Increase your ISO by one stop - ISO 200 to 400, say - then double your shutter speed - 1/200th of a second to 1/400th - and your exposure will stay the same. You increased by a stop, then decreased by a stop. Aperture is more involved, so we’ll get to that another day.

Okay. How are you doing? That’s quite a bit to plow through. If you made it all the way, give yourself another cup of tea. You earned it.

See you back here for part two!