In this part, let us understand how we can use the Aperture settings to achieve required Depth of Field (DOF) in an image.
Depth of Field (DOF)
Depth of Field refers to nearest to the farthest object that is acceptably sharp in an image.
As we understand that image is a 2-dimensional representation of a 3-dimensional medium (width, height and depth).
Just take a look at the scene right in front of you. You can see the objects in their 3-dimensional format. Isn’t it? You can see from few inches in front of you to the farthest object which might be few feet or meters away.
How much can you see from immediate foreground to the background sharply? If you see everything sharply, then your eye has Deep Depth of Field. Which means everything from foreground to background is in clear focus.
Try this now. Bring your thumb as close as possible to your eyes. Concentrate on thumb only, now what do you see?
Do you see only thumb in clear focus and rest blurred? If so, then your eye has Shallow Depth of Field. This means, only one object is in clear focus and rest of the scene falls out of focus.
Let us examine how we can achieve the shallow or deep DOF in photography.
Factors Affecting Depth of Field
There are several factors that affect how much DOF one can achieve. They are:
- Aperture (f-stop)
- Camera-to-Subject distance
- Subject-to-Background distance
- Len’s Focal Length
- Sensor Size (Full-size or Cropped sensor)
- Circle of Confusion Criterion
For now, let us consider only the Aperture and its effect on Depth of Field. We will consider all other factors along with Aperture to illustrate how they affect Depth of Field in a dedicated article.
Shallow Depth of Field (DOF)
An image is said to have shallow DOF when only a small portion of the image (generally main subject of interest) is in sharp focus, but rest of the scene is out of focus.
Shallow DOF yields to aesthetically pleasing images due to the bokeh effect produced by out-of-focus areas. It is extensively used in Macro, Portrait and Wildlife Photography especially in Bird photography.
Shallow DOF can be achieved with larger aperture values (smaller denominator values) like f/2.8, f/4, f/5.6, etc. It’s that simple! Provided all other factors are taken care of. But there are some exceptions, which you can see in the below photographs!
Below are some photographs where I have used Shallow Depth of Field.
Deep Depth of Field (DOF)
An image is said to have deep DOF when the image is in sharp focus from foreground to background.
Deep DOF is much widely used in Landscape Photography where it is usually necessary to show the entire landscape in sharp focus. However, sometimes keeping only portion of the landscape image in sharp focus yields wonderful image (Tulip garden image).
Deep DOF can be achieved with smaller aperture values (bigger denominator values) like f/9, f/11, f/16, f/22, etc. Here again, we need to take care of all other factors. But there are some exceptions, which you can see in the below photographs!
Below are some photographs where I have used Deep Depth of Field.
Simple Experiment to see the effect of Aperture
Try out this simple experiment to see the effect of Aperture on Depth of Field.
- Setup the Camera on Tripod or a sturdy surface.
- Place the main subject of interest like a flower, vase, or a toy at around 5 to 8 feet from the Camera.
- Make sure there is atleast 10 feet distance between the main subject and the background.
- Compose the scene as you wish.
- Dial the aperture down to the largest f-stop (like f/2.8, f/4, f/5.6).
- Focus on the main subject.
Now take photographs with different aperture settings (f-stops) starting from the largest aperture to the smallest aperture.
If you take a look at the photographs you will see the Depth of Field increases as you go from larger aperture values (small f-numbers like f/2.8, f/4) to smaller aperture values (big f-numbers f/16, f/22). But there are some exceptions, which you can see in the below photographs!
To make this experiment more interesting, you can place a foreground object and a background object. In this way, you could see how foreground object and background objects come to focus as you choose smaller aperture values.
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