Exposure triad: aperture, shutter speed and ISO

As we mentioned on the previous post about exposure, we will make our pictures have the perfect light thanks to the exposure triad, what does this means? This makes reference to three different settings: shutter speed, aperture, and ISO. And we’ll have to play around with them, not just to get the perfect exposure, but also to get the composition as we wanted it to look like. Are we aiming to get a blurry backgroud? Maybe we want to freeze movement, or make it blurry? Are we shutting with really low light conditions?

Shutter speed

The shutter speed is a small set of curtains that are in front of the sensor, I always picture them in my mind as eyelids. When you have your eyelids open, your eyes get the light in, and your brain register what you’re seeing, right? As soon as you blink, the information gets recorded. That means that the shutter speed is what allows light to go to the sensor and record the image during a certain amount of time, usually seconds, or fractions of a second.

The most important characteristic about the shutter speed, and what we have to have in mind while we are working, or composing our picture, is how it works with movement. The higher the shutter speed number is, the longer the light will be entering in the camera and recorded on the sensor, which means we’ll get blurry motion. On the other hand, the lower it is will give us a really fast picture, that will freeze motion, which might look amazing or be necessary.

Shutter speed and motion
Shutter speed and motion

In general, usually a range of 1/125 second or 1/160 second will be safe enough to shoot without needing a tripod, and if you want to do longer exposures, well… tripods aren’t that expensive, and we all want to play along with the exposure sometimes, right?

Aperture

The second big one we have will be the apertureI like to think about aperture as if it was the pupils of the camara, the more dilated and open it is, more light will go into the eye, or in this case, the lense, and get into the sensor. In this case, the aperture would be how much does the diaphragm of the camera opens for a particular picture.

Any special powers of aperture? Of course! We have to pay attention to the aperture when we are working on the depth of field, and what does it mean? This means how much do we want the background to be sharped or blurry. The way we get that is by using a smaller aperture for the times we want everything on focus, and a higher aperture, when we want the subject of the picture being in focus and the background blurry.

ProfundidadDeCampo
Aperture differences on depth of field

ISO

The ISO is basically what we need to get more light into the picture when we’re shooting in low light conditions. It is pretty amazing because each time you upgrade it to the next leverl, you automatically double the amount of light that’s going to be in the picture. Downsize? That the higher the ISO goes, there will be more grain in the picture, which most of the times will ruin the picture, at least most of the times, as you may be going for that feeling.

ISO
ISO grain

How do I make it work then?

Well, basically what we have to think first is paying attention on how do we want our picture to look like, do we want to pay attention to the depth of field, the motion? Imagine we’re doing a portrait outdoors, we’ll give more importance to the subject and we might want the background to be blurry. Are we shooting sports? Then we may have to pay more attention the shutter speed so the image doesn’t gets blurred. What if I have set my camera as I want with the aperture, because the depth of field is exactly how I want to, and I can’t change either the shutter speed because it will get blurry? Then you’ll have to set your ISO higher to compensate, being careful with the grain.

You can use this page to get a hint of how this works.

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