The basics of photography

Any photographer wishing to get out of automatic mode has had to integrate technical notions of photography before being able to play with them in order to progress and create the desired effects. These technical basics come from the realms of physics and chemistry, followed by the academic basics (rules of thirds, perspective, etc.). There are three important principles to take into account when starting photography and getting the right amount of light: sensitivity, aperture and shutter speed.

Sensitivity (ISO or ASA)

In the past, in film photography, the film contained silver grains that reacted to light (hence the importance of chemistry). When light «hit» the grains, they darkened; without light, they did not react (hence the negatives). The concept remains the same with the transition to digital; the silver grains are simply replaced by sensors. These sensors—or grains—have a certain sensitivity to light, indicated by the ISO rating (known as ASA in the film era). The higher the ISO, the more sensitive the sensors are to light, so less light is needed; conversely, the lower the ISO, the less sensitive the sensors are, so more light is required.

For a landscape shot in Barcelona’s bright sunlight, choose a low ISO setting—for example, ISO 100—to avoid an overexposed (too bright) photo. For a concert in low light, use a high ISO setting, such as 6400, to ensure the photo isn’t underexposed (too dark). The ISO setting also affects noise (a «pixelated,» grainy effect). If the ISO is low (a small number), there will be little noise. Conversely, if the ISO is high (a large number), there will be more noise. Therefore, a low ISO setting is preferred for architectural photos where details are important. The impact of noise is still negligible, however.

Aperture Size

The aperture is the equivalent of the eye’s pupil; it must adjust to the light. In bright sunlight, a small aperture is needed to let in less light, and in dim light, a large aperture is needed—always with the goal of achieving a result that is neither overexposed nor underexposed. The f/2 setting corresponds to a large aperture, while f/16 corresponds to a small one.

The aperture setting affects the depth of field (the importance of physics)—that is, the area in which the subject of the photo will be in focus. A wide aperture (low number) creates a shallow depth of field. We therefore choose this setting for portraits to achieve an «artistic blur,» or «bokeh,» in the background. Conversely, a small aperture (high number) creates a large depth of field: we generally use this for landscapes to ensure sharpness across all planes.

Shutter speed

Also known as the exposure time, this is the length of time during which light strikes the sensors. If there isn’t enough light, the shutter speed will need to be slower (1 sec) than if there is plenty of light (1/2000 sec). This setting allows you to create an impression of stillness or motion. If you want to photograph a cyclist moving at high speed and want the subject to be in focus, a fast shutter speed is necessary. If you want a motion blur effect, you’ll want to use a longer exposure time.

The next time you take a photo, focus on the effect you want to achieve. Make the appropriate adjustment and tweak the other settings to achieve the correct exposure. From now on, you can stop using automatic mode and precisely control how your photos turn out.