Playing with depth of field is one of the most widely used fundamentals of photography to achieve creative result. Photographers isolate their subject or create a stunningly end to end sharp landscape by manipulating the depth of field. One of the key tools to play with the depth of field is your aperture settings. A wide aperture will give you a shallow depth of field and a small aperture will result in a deep depth of field. Well let’s first understand what depth of field is.
When you focus your camera to a particular subject, the camera establishes a plane of focus. Basically it is a virtual parallel line in front of your camera where the subjects falling on that line will be sharp. Along with this, there will be some area in front of that line and behind the line which will also be sharp. Depth of field is the distance in front of and behind the subject which appears to be in focus. Technically only the subject where the camera focuses is truly in focus. But because the focus falls of gradually there is still a region extending in front of and behind the subject which appears to be visibly sharp.
Let’s understand why this happens. When the light enters the camera with a larger or wider aperture, it needs more bending to meet at a single point at the camera sensor. Because these lights bend more, they intersect at a greater angle. There are many light rays passing through this process far from the optical axis of the lens. The lights which converge before or after the image plane becomes softer. Therefore it appears to be out of focus. Similarly when the aperture is narrow or small the light passing through the aperture is closer to the optical axis and not refracted much. The reduction in refraction means that the defocused lights are closer when they intersect before or after the image plane which results in a smaller angle. This smaller angle creates smaller blurry spot hence gives deep depth of field. 
Let’s see a practical example of a particular subject with different aperture settings.
Now that we understand the aperture is one of the key elements to control depth of field, let’s discuss some of the practical application of it. There are situations where we want to attract the viewers attention to a particular subject hence we would want to isolate the subject from rest of the elements in the frame. For example, Portrait, Wildlife close-up, Sports, etc. We can achieve this by using a wider aperture. Similarly landscapes, a big group photograph, architecture, products photography needs a deep depth field hence we should use a smaller aperture. The possibility of creativity in an image with the play of depth of field is huge. It all comes down to the photographer’s imagination. Therefore always ask yourself, what you want to show and how aperture can play an instrumental role to achieve your visualized image.
