Depth of Field (DoF) can have positive and negative effects; knowing exactly what it does and how to control it is essential to taking the best possible photos. This post teaches you all about how to use it to your advantage and how much DoF is right for different situations.
What is Depth of Field?
Depth of Field (DoF) is the distance between the closest objects in focus and the furthest point of focus. This distance can be increased or decreased by changing the aperture of the lens. You’ll often see shallow DoF used creatively in photos as it forces the focus onto a certain point of interest.
How does it work?
DoF is controlled by the width of the aperture in the lens. For those of you who don’t understand aperture, I strongly suggest going back to read this post first. The wider the aperture, the shallower the depth of field and vice versa. The diagram below explains this.
To really get a strong sense of why this is, have a look at the diagram I made below.
The wide aperture, which goes from the full width of the lens, takes in light at a much wider angle. This, in turn, means that the light has less distance to travel before it becomes out of focus. A narrow aperture, on the other hand, stays in focus for much longer as the light has to travel further before going out of focus.
That’s not all that affects DoF though, there’s also the focal length and distance from subject.
Distance from Subject
The best way to demonstrate this is not with a diagram but with your own hand.
Take your arm and stretch it out in front of your face with your hand as far as you can reach. Looking at your hand you’ll notice that you can still work out a lot of detail behind it without moving your eyes away. Now, gradually move your hand closer to your face all the time focusing on it and you’ll notice that your peripheral vision will get more and more out of focus.
The same effect is present when using a camera lens.
Creative uses of DoF
Shallow DoF is often used to create a point of focus on one single subject in a photo. It’s hugely effective at doing this and has become quite common with the availability of cheap wide aperture lenses.
I recommend playing around with shallow DoF’s but be careful not to overdo it as your photos will become boring and similar. It’s an easy effect to achieve which means that a lot of people will be doing it, yet it can be very effective – try to go further than this to put yourself above the rest.
Extremely shallow DoF shot at f/1.4
Using an aperture this wide creates really nice, soft photos. When shooting in the evening sun, it can be used to make a photo look much warmer. Notice how the face is sharp but the neck and shoulders appear quite soft.
It’s also fun to play around with the focal plane when the DoF is this shallow: in this photo I placed the flower to the right of her face so that it was also in focus. I was able to achieve this easily as I wasn’t too close to the subject and the lens I used was only about 50mm.
Shallow DoF shot at f/1.8
This shot was taken in the evening with the sun nearly gone; part of the reason the DoF was set so low. It’s a really good way of getting smooth, soft photos where there is still a point of sharpness and detail. Because the focal length was effectively about 75mm and I was very close to the object, the DoF is exaggerated.
Medium DoF shot at f/5.6
With an aperture of f/5.6, you can clearly make out the detail of the whole body as well as some of the background. In situations like this where there is depth to the photo, it’s important to consider the aperture before taking the photo as you’ll want to keep as much of the subject in focus as possible.
Deep DoF shot at f/22
For many ‘scene’ shots, you’re going to want to keep as much of the scene in focus as possible. This means using a narrow aperture and a deep DoF, allowing the viewer to explore the entire photo. I chose this as an example as you can clearly see that there’s a lot of depth and plenty of places for your eyes to wander.
If you’re having trouble understanding any of this, I strongly suggest you read the 3 articles linked inside of this post.
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