It’s easy to have the mistaken impression that photography is all about cameras. But a camera is actually just a tool which 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 tiny 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 gagetry to create a photo!
That’s all pretty esoteric, so why did I go into it?
Because knowing that photography is all about light, and that your camera is at its core 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. In order for a photo to be properly exposed all three legs of the stool must be the same length. If you make a change to one leg without adjusting the others to balance it out your stool becomes tipsy. You end up with an over or under-exposed photo. (Too bright or too dark.)
The aperture on a lens is the hole that allows light in to 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 budget point and shoot camera might have aperture sizes ranging from f4 to f8. A high-end DSLR lens might go from f1.4 to f32.
Aperture size can affect image quality. Many lenses have a “sweet spot” that produces the sharpest photos, often around f8. You won’t know your camera’s sweet spot without experimenting.
Aperture size also affects depth of field (DOF). DOF is its own entire topic, but I’m briefly mentioning it here so you know that aperture doesn’t only affect quantity of light. With large apertures you have a shallow DOF, meaning less of the photo is in focus in front and behind the subject. A small aperture has a big depth of field and most or all of the photo will be in focus.
The basic thing to remember about aperture as a beginner is:
Small number = more light.
Large number = less light.
Remember the shoebox pinhole camera from above? The pinhole punched into the box is the aperture. The flap covering the hole is the shutter, just like a shutter on a window. While shutters in cameras are much more sophisticated than a flap of cardboard, the end result is the same.
The lens shutter opening and closing again controls how long light is allowed to enter the camera through the aperture/hole.
In most situations shutter speeds are measured in fractions of a second. The higher the number is after the slash, the faster the shutter opens and closes. A typical shutter speed is 1/250 of a second. With night photography shutter speeds are usually measured in full seconds.
For the basics, 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 shows up by making your picture look out of focus.
Many mid-range and most high-end cameras have some kind of stabilization technology (IS = image stabilization, VR = vibration reduction) built into the camera body or lenses. This tech counteracts the shake from your hand, giving you crisper images at slower shutter speeds. Image stabilization is not only useful for dim lighting conditions, but is also helpful for people with hand tremors.
How slow of a shutter speed you can get away with using hand-held depends on how steady your hands are. Without IS I struggled getting crisp photos with anything less than 1/125, but steady hand people routinely use 1/80 or even 1/60. With really good IS some people use as slow as 1/5 with adequate results.
2.) The other important aspect of shutter speed is freezing action. If a subject is moving at all, the longer your shutter is open the more of that movement you will record as blur. Sometimes capturing motion blur is intentional on the part of a photographer. But in typical situations motion blur is cause for disappointment.
Moving subjects can be anything from a flower swaying slightly 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.
Typical shutter speeds for stationary subjects are 1/125 and 1/250. For people or animals moving around you’ll usually want at least 1/500. 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 or the origin of the term since it’s boring and knowing doesn’t help you take pictures.
ISO can be the trickiest of the triangle to grasp because it isn’t an obvious mechanical function like aperture size and shutter speed. The ISO scale relates to the camera sensor’s sensitivity setting.
The ISO scale typically 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.
The sensitivity being measured is how quickly responsive to light the camera’s sensor is.
A low ISO setting means that more light is needed for a properly exposed photo. A high ISO means less light is needed to capture a properly exposed image.
A first response to this might be, why not just set it to a higher number/sensitivity and then never have to worry about it?
Because, increased sensitivity degrades image quality (IQ). The price for that highly sensitive quickness is “noise.” (The grainy dots or flecks seen in digital images.)
How much you can increase ISO before seriously degrading the image is dependant on your camera model. You will have to experiment to discover what is acceptable to you. As a general rule of thumb, the more expensive a camera is the better it performs at higher ISO settings.
The basic thing to remember about ISO as a beginner is:
Lower ISO numbers are better. Use your camera’s lowest native ISO number whenever possible.
When that isn’t possible is when not enough light is coming through due to the aperture and shutter speed being used.
Aha! There it is. The triangle. Aperture, shutter speed, and ISO all control light, and all work together to expose a photograph.
How the Triangle Works Together
Remember, it’s all about light.
On bright sunny days there is plenty of light, which means for most photographic purposes you can do what you like. You can use your aperture sweet spot, a medium shutter speed, and a low ISO. This will provide the best image quality your camera is capable of producing.
It’s when you have less light to work with that the balancing act of the three-legged stool really comes into play and you have to start thinking 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 subject is in focus.
* Slowing down the shutter speed lets in more light, which allows you to use a smaller aperture in order to maintain enough DOF for your subject.
* 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 increases the amount of noise in the 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.