Are you interested in photography but the technical aspects seem too abstract to you? This article is for you! Three one-minute videos to understand aperture, speed and learn how to use these parameters to take successful photos.
Before going into the purely practical part, I will focus on the theory. I think it is important to understand how the parameters work, without going into physical principles or mathematical calculations, so that I can then be able to choose how they will influence the picture.
The exposure triangle: iso + aperture + shutter speed
A perfect exposure is when you can do what you want, and in 90% of the cases, it will be a question of having a photo that is neither too light nor too dark. (I’m not going to start confusing you right now with the exceptions!).
To do this, we’re going to play with three parameters: aperture, speed and ISOs. The third being the one that interests me the least, I’ll start with it: the ISOs correspond to the sensitivity of your sensor. The higher they are, the brighter the rendering will be. This is a setting that will interest you especially in dark places where you can’t help but increase the ISOs.
As a side effect, raising the ISOs increases the noise (those ugly little pixels you see especially in dark areas). This noise can be attenuated by software, but you will still be advised to stay on low ISOs as much as possible. Do the test with your camera, but on a small entry-level SLR, I only go up to 1600 if absolutely necessary, and I usually stay between 200 and 400 for daytime outdoor photography.
Understanding the aperture
Let us now turn our attention to the opening. This refers to the amount of light that will reach the sensor.
It can be adjusted on the body (apart from a few rare manual lenses) but will be limited by the lens: not all lenses allow large apertures. This is the number that is given next to the focal length indications. For example, a 24-70 2.8 is a zoom that goes from 24mm to 70mm and opens to 2.8. The diaphragm is located in the lens, it determines the size of the hole to let the light pass through (not to be confused with the shutter).
The small trap is that this 2.8 is actually a fraction: 1/2.8, which means that the smaller the number, the larger the aperture. So a 50mm 1.4 is brighter than a 50mm 1.8.
The aperture will therefore be large on two points. On the one hand, the wider you open, the less time you need to open. That is to say that for the same exposure, I can choose between letting in a lot of light, or letting it in for a long time. We’ll see in the section on speed what effects this can have on the image. On the other hand, it is the aperture that will determine the “blur”.
Understanding (shutter) speed
The shutter speed is the time from the time you shoot to the time the shutter closes. Specifically, it is the time during which the sensor is exposed to light.