It’s easy to get the mistaken impression that photography is all about cameras. But a camera is actually just a tool that gathers light.
The (abbreviated) definition of photography is: The art or process of producing an image by the action of light.
The word photograph itself comes from the Greek words photo, meaning light, and graph, which means write. A photo print is essentially light written onto a piece of special paper.
To prove the light gathering tool concept, you can make a camera out of a shoebox. All you need is a piece of photosensitive paper attached to the inside of one end of the box, a pinhole in the center of the other end, and a flap to cover the hole. When you open the flap over the hole, light enters the box and an image is recorded on the paper. No need for lenses or electronic gadgetry to create a photo!
That’s not very practical info, so why did I go into it?
Because knowing that photography is all about light, and that your camera is just a fancy light gathering tool, will help you understand the exposure triangle. The exposure triangle is the basis of all photography.
The exposure triangle is: aperture, shutter speed, and ISO.
Think of the exposure triangle as a three-legged stool. The stool needs all three legs to be the same length to be safe to sit on. If you make a change to the length of one leg without adjusting the others to balance it out your stool becomes tipsy.
Aperture, shutter speed, and ISO work together to make a balanced exposure. If you make a change to only one of them you throw off the balance. Changes to one require other changes to compensate and even it out again.
The aperture on a lens is the hole that channels light into the camera to expose the digital sensor. Larger holes allow in more light, smaller holes allow in less.
Aperture size is measured on the f-stop scale. Thankfully we don’t need to know the math and physics behind the f-stop scale in order to take good pictures. All you need to know is what the numbers mean in practical terms.
It’s a little confusing at first because small f-stop numbers (like f2) are large apertures, and large f-stop numbers (like f16) are small apertures.
A point and shoot camera might have aperture sizes from f3.5 to f8. A DSLR (digital single-lens reflex camera) lens might go as low as f1.4 or as high f32.
Aperture size can affect image quality (IQ). Many lenses have a “sweet spot” that produces the sharpest photos, usually around f8. You won’t know your lens’s sweet spot for sure without experimenting.
Aperture size also affects depth of field (DOF). DOF is its own separate topic, but I’m mentioning it here so that you know aperture size doesn’t only affect quantity of light.
The basic thing to remember about aperture as a beginner is:
Small number = more light.
Large number = less light.
Remember the shoebox pinhole camera? The hole punched into the box is the aperture. The flap covering the hole is the shutter, just like a shutter on a window. Shutters in cameras are much more sophisticated than a flap of cardboard, but the end result is the same.
The camera shutter opening and closing again controls how long light is allowed to enter the camera through the aperture.
Shutter speeds are usually measured in fractions of a second. The higher the number is after the slash, the faster the shutter opens and closes. A slow shutter speed is 1/20 of a second. A typical shutter speed is 1/250. A shutter speed of 1/2000 is very fast. With night photography shutter speeds are measured in full seconds, not fractions, because there is very little light.
Shutter speed is important in two ways:
1.) When hand-holding a camera there is always some amount of camera shake because it is impossible for your hand to hold completely still like a tripod. When a slow shutter speed is used this camera shake makes your picture look out of focus. Fast shutter speeds open and close the shutter so quickly there’s not enough time for camera shake to show up in your photo.
Image stabilization (IS) technology built into cameras and lenses can reduce or get rid of camera shake, giving you crisper images at slower shutter speeds.
How slow of a shutter speed you can use depends on how steady your hands are, your shooting technique, your lens, and if your gear has IS. You will have to experiment to see what your personal limit is.
The basic guide for lenses is that wide-angle lenses cause and capture less camera shake, so they can be used with slower shutter speeds. Telephoto lenses are harder to hold steady and show camera shake easily, so need faster shutter speeds to overcome it.
2.) The other important aspect of shutter speed is freezing action. If a subject is moving, the longer your shutter is open the more of that movement you will record as blur in your photo. Sometimes capturing motion blur is done on purpose. But in most situations motion blur is unwanted.
Moving subjects can be anything from a flower swaying in a breeze to fast action sporting events. The more a subject is moving the faster your shutter speed needs to be for a sharp photo.
For a beginner’s guide: Shutter speeds for non-moving subjects of 1/125 and 1/250. For people or animals moving around, at least 1/500. Birds in flight 1/2000. A professional sports photographer might use 1/4000 to capture the action.
The basic thing to remember about shutter speed as a beginner is:
Very slow shutter speeds require a tripod to eliminate camera shake.
Medium speeds are good for average photos.
Fast shutter speeds are needed for quickly moving subjects.
To sum up at this point: Aperture controls the amount of light let in. Shutter speed controls how long that amount of light is let in.
ISO is pronounced as a word: eye-so. Many say it as an acronym, but that’s not technically correct. I won’t get into why since it’s boring and doesn’t help you take pictures.
ISO is the trickiest of the triangle to fully understand because it isn’t a mechanical function you can see like aperture size and shutter speed.
Most info on the web incorrectly describes ISO as the light sensitivity of a sensor because that is how film works and it’s a relatively easy concept to grasp.
However, the actual explanation for camera sensors has something to do with photons, electrical signals, and other incredibly technical stuff. It isn’t useful information for anyone who isn’t an electronics expert.
So rather than getting hung up on what ISO really is, let’s discuss how it’s used in practice.
The ISO scale usually starts at around 100 and goes up to 64,000 or higher, but it varies. Different camera models have different starting points at the low end, and only expensive cameras offer the high end.
A low ISO setting means that more light is needed for a properly exposed image
A high ISO means less light is needed to capture a properly exposed image.
An understandable response to this is, why not just set ISO to a higher number and leave it there so you never have to worry about it?
The answer is, increased ISO can degrade image quality. The price for high ISO is loss of detail and “noise.” (The grainy dots, blobs, or flecks seen in digital images.) The higher ISO is set the more potential there is for noise to appear in an image.
How high you can set ISO before ruining an image depends on your camera model and how much noise you can personally accept. With some cameras 800 might be too high, and in others 3200 might be safe to use. It can also vary somewhat depending on what you are photographing. An ISO of 1600 might look acceptable in one photo but not so much in another.
You will have to experiment with your particular camera. As a general rule of thumb, the more expensive a camera is, and the larger the sensor is, the better it performs at higher ISO.
The basic thing to remember about ISO as a beginner is:
Low ISO numbers are better. Use your camera’s lowest ISO number whenever you can.
When you can’t is when your aperture and shutter speed aren’t letting enough light into the camera.
When that happens, set ISO to a higher number to compensate.
How the Triangle Works Together
Remember, it’s all about light.
On bright sunny days there is plenty of light, so you can do pretty much whatever what you like with your camera settings. You can use your aperture sweet spot, a medium to fast shutter speed, and a low ISO. This will provide the best image quality your camera can produce.
It’s when you have less light to work with that you have to think about where to compromise.
* Increasing the size of the aperture lets in more light and allows you to use a faster shutter speed to keep photos free of motion blur.
* Large apertures have shallow depth of field, which means less of your photo is acceptably in focus.
* Slowing down the shutter speed lets in more light, which allows you to use a smaller aperture for more DOF.
* Slow shutter speeds can capture motion blur, making your photo look out of focus.
* Increasing ISO allows you to “cheat” light conditions by continuing to use a smaller aperture and faster shutter speed than the light conditions would normally allow.
* Increasing ISO can increase the amount of noise in an image.
I figured it might be helpful to post some examples, but it was pouring rain all day yesterday. I ended up in my building’s parking lot in order for me and my camera to stay dry under an overhang! So excuse the crummy examples. Especially since I ended up having to do major cropping in order to show enough detail, and cropping reduces resolution. But these will at least provide the general gist.
(Note: You can click on the photos to get a better look, but after posting this I realized WordPress isn’t displaying these at full resolution, so a lot of the detail is lost when you zoom in. This makes the examples less useful because Photo 1 doesn’t look as sharp as it should, you can’t clearly read the sign, and the noise and loss of detail in Photo 4 doesn’t look as bad as it should.)
Photo 1.) This shows settings so the camera performs at its best in good light: f8, 1/400, ISO 160. Even though I used a lot of zoom on my lens details are clear, you can even zoom in on the photo enough to read the sign in the background. (The ferry is distorted due to atmosphere, not the camera, as the water was warmer than the air.)
Photo 2.) I set the camera to automatic to let it choose all the settings. It’s slightly under-exposed, but details are okay even after major cropping. Though it was gray and raining you can see there was still enough light for the camera to use settings with no major compromises for this scene: f3.3, 1/200, ISO 125. Notice the falling rain isn’t visible due to a slower shutter speed.
Photo 3.) I cranked the shutter speed up to 1/1000. The camera had to adjust by raising the ISO to compensate for less light entering. The aperture was already wide open. If you zoom in you can see raindrops in mid-air because the fast shutter was able to capture them. Also look at the black car behind. There’s quite a bit of noise due to the higher ISO. f3.3, 1/1000, ISO 800.
Photo 4.) I boosted the shutter speed even more. This time the ISO went up to 1600 to compensate. Zoom in to look at the black car behind. There’s so much noise that details are all smeary. (Noise shows up the most in large areas of solid color.) f3.3, 1/2000, ISO 1600.
Photo 5.) I slowed the shutter way down to 1/25. I turned the IS (image stabilization) off. I was surprised this turned out as clear as it did at such a slow shutter speed, but if you zoom in you will see details are soft due to camera shake. Since a lot more light entered with the slow shutter speed the camera closed the aperture down to its smallest size and reduced ISO to the lowest number. f8, 1/25, ISO 80.
The purpose of this post was to explain the exposure triangle in photography. I didn’t go into details of how a beginner should use their camera settings to make changes to the triangle because that’s another entire post.