Depth, well, it is one of the words that is analogous to many other things. While all the other secondary meanings of the word are related, the primary meaning would be ‘the distance between the top and bottom surfaces’. Even when it comes to a movie, the depth becomes a lot of things too. For suppose, the depth of a film can indicate the story going to deeper levels or the subject of the movie being deep. But we are particularly talking about the depth of field!
But technically, or to say, visually, depth or precisely depth of field is something that deals with focus. Depth of field is the field of vision that is in focus in a particular shot. Different camera lenses allow a certain depth of field. The aperture of a camera lens decides the amount of light that the sensor captures. Hard to understand, right? Let us break it down!
How does a camera function?
A camera is something that captures light through sensors. When you click the capture button, the light reflecting from the subject falls on the sensor. The shutter closes, and the captured light develops an image. Cameras are something that can control time with light. You can capture a moment of running time, and you can freeze that particular moment and hang it in your homes.
Aperture is the hole of the lens. The light that passes from the subject is passed through the aperture of lenses before hitting the sensor. You can adjust the size of the aperture, and it affects the photo differently. When the aperture (opening) of the camera is wide open, it lets in all the light coming from outside. When more light falls on the sensor, only the subject appears clearly, and the rest of the background becomes blurred.
Because of the vast light that is going in through large aperture, this blurring of the background happens. And the blur occurs because the background is not in the depth of field. Depth of field is the area of focus in an image or a video. By making the aperture wide open and letting in more light, you decrease the area of focus, and only the subject of the image appears clearly.
Similarly, if you decrease the size of the aperture, the light hitting the sensor is reduced. By each point of decrease in the aperture, the area of focus begins to increase. And if you tighten the aperture to the largest and closest, you can observe that now even the background is clear and not blurry. This blurring and focusing of subject and background happen because of the light going in and hitting the sensor.
F – stop
Something much more critical and confusing here is that the values of changing the aperture are referred to as ‘f-stops’. If you change the f-stops, the aperture either increases or decreases as per your requirement. The f-stops are fractions and are measured as f/1.8, f/2.8 and may have greater f-stops till f/22 or even higher. The common mistake one can commit while talking or understanding f-stops are about how they impact aperture.
It is clear to use that if aperture (hole) is wider then it lets more light in and the depth of field (area of focus) decreases. And if the aperture is close and tight having a smallest possible opening, it only lets little light and the depth of field increases. The f-stops with smaller numbers indicate wider aperture and the ones with bigger numbers indicate tighter aperture.
It is that, greater the number of f-stop, lesser the opening of the aperture. And lesser the number of f-stop, greater the opening of the aperture. So, if you want to take a picture focusing only the subject and blurring out the background, you should choose lesser f-stop number on camera as it means that you are widening your aperture and letting more light. Thus, decreasing the area of focus, i.e., depth of field!
We have discussed how the depth of field is created, shifted and used to take pictures or videos. In the following week, let’s get into the practical use and ways of depicting the depth of field. We shall also see different types of uses of the depth of field to tell stories visually.