After you bought your first DSLR and a lens or two, you may find yourself feeling a bit awkward every time you use your camera in the “green” Auto-mode. You wish to be one of those photographers who change their camera settings on the fly to get those awesome shots. You envy a bit those guys who know their cameras from the inside out and who always override the Auto-mode suggested settings. And it turns out that they know what to do better than their cameras. If this applies to you, then it’s time to move forward from the Auto-mode. And the first thing you need to understand to become a better photographer is exposure.
There are three elements that exposure consists of. These are shutter speed, aperture and ISO. Let’s start with the first one. Every time you press a shutter to take a photo, your camera opens a set of curvy “curtains” to let the light from outside to hit the camera sensor. Shutter speed is the time that these curtains stay open. As simple as that. Shutter speed is measured in fractions of a second and can be extremely fast (1/4000 of a second – for freezing some action) to extremely slow (30 seconds – for long exposure night shots). One of the main things to remember is that if you shoot without a tripod, don’t go slower than 1/100 second shutter speed. Otherwise your photos will come out blurry. Some people would shoot at 1/60 using camera image stabilizer, but 1/100 would be the safer threshold.
The second element forming your exposure is aperture. If you have seen photos where the subject on the foreground is in sharp focus but everything on the background is nicely blurred – this effect is controlled by changing the aperture. Aperture controls the depth of field (DOF – you will see this abbreviation a lot). Depth of field means how much of the image is in focus. You can control this by setting for example the depth of field to be 3 meters all around the focusing point (your subject). Physically aperture controls how wide your shutter curtains open when you press the shutter. Aperture is measured in f/numbers. Pay attention that a smaller number (like f/4) means more light hitting the sensor and shallow depth of field; when a larger number (like f/22) means less light hitting the sensor and larger depth of field.
The third part of the exposure triangle is the ISO setting. This setting came from film camera times and it literally means film sensitivity to light. Nowadays it’s been transformed to sensor sensitivity. Back in a day you would need to load different film into the camera in order to change this setting, today you can choose it on the fly by just clicking a button. Lower ISO setting (like ISO 100) will return you images with least digital noise, but you would you’re your subject to be well lit to take a photo. Greater ISO settings (like ISO 6400) will allow you to shoot almost in complete darkness, however, your photos will have quite a lot of digital noise which you would need to fix in post-processing. If you wonder what the digital noise is – it’s the effect when you have dark areas of your image covered in tiny dots. Rule of thumb for ISO settings is to shoot at as low ISO as you possibly can. However, in a very dark environment, if you don’t have a tripod with you, your ISO needs to be cranked up as it’s the only way to make anything on the image to be visible at all.
So, here is the Exposure triangle – shutter speed, aperture and ISO. We suggest you start off with using either shutter speed priority mode or the aperture priority mode – set one of these manually, leave the other one for the camera to auto-set it for you. Review your photos and you will see how one setting affects another, it will help you to get a better feel of how your camera works.