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Understanding Depth of Field
A guide to mastering depth of field in photography!
Understanding depth of field is a crucial part of learning to take better photos. It's one of the key things that shape the style and mood of a photo. Using your digital camera settings to set the depth of field will give you a lot more creative options when capturing different subjects.
Even when the camera is pointing at the same thing, a difference in depth of field can radically change the subject, feel and aesthetics of a shot. But what is the difference between a narrow depth of field and a large one? What factors produce the depth of field and which kinds of shots suit certain depths of field?
What is depth of field in photography?
When you focus your camera on a specific subject you know that part of the photo is going to be sharp. But a certain amount of space surrounding the subject remains in sharp focus too. The size of this area is referred to as the depth of field.
The depth of field is not a clearly defined area, but merges gradually into the blur. The 'blur' outside the sharp depth of field area is sometimes called 'bokeh'.
Bokeh can often look very cool and is an important part of a photo in itself (e.g. bright city lights that become big, round, colourful dots), even though it is out of focus.
Understanding depth of field: What factors determine it?
The key to understanding depth of field is to know what causes some photos to have a narrow depth of field and some to have a large one. Then you can start controlling the appearance of your shots with ease!
- The first factor is the size of the aperture. This is the key one. Just remember: Big aperture - small depth of field / Small aperture - big depth of field.
So a big aperture (small f. number), which admits lots of light into the camera, will produce a shallow depth of field. Meanwhile a little aperture (big f. number), which admits less light into the camera, will produce a large depth of field.
Understanding depth of filed is much easier when you see examples. The photos below were each taken with a different aperture setting. Notice how a larger aperture / smaller f. number produces a more shallow depth of field:
Aperture: F 4.5
Aperture: F 8
Aperture: F 16
- The next important factor for understanding depth of field in photography is something called ‘focal distance’. Basically: how far away from your subject are you standing?
Right up close? That's going to reduce the potential depth of field. Standing back, for a landscape perhaps? That enables a big depth of field. If you think about it that's just how our eyes work!
Hold your hand close to your face and focus on it. See how even nearby things become blurry - or bokeh! Now look out the window and check out stuff in the distance. It's all pretty clear, right? Understanding depth of field is pretty simple really!
Let's take a look at the above picture on aperture f.16 compared with another shot taken with the exact same setting, but just from further away.
Can you see how the flowers behind are clearer in the second shot?
Aperture: F 16
Aperture : F 16 + Greater Focal Distance
- The final factor that impacts depth of field in photography is 'focal length'. Focal length is different to focal distance. It's basically the amount you are zoomed in on your subject.
To be honest, it's actually a bit of a misconception that focal length determines depth of field. The aperture size and focal distance are the key things. But what focal length does do is appear to influence depth of field - so it's still quite important.
Why does is appear to? Think about it, when you zoom in with your lens the background becomes larger in relation to the foreground than when you take a photo with a wide angle of view. It looms larger behind the subject.
Since the background is out of focus this gives more prominence to the blurry part of the picture than when there is a small focal length. So photographers often like to use telephoto lenses to enhance the sense of a narrow depth of field and isolate the subject from the background.
Understanding depth of field: When to use the different options?
First up, the whole point of depth of field is that it gives you more creative freedom when taking pictures. So there are certainly no rules about when to use a shallow depth of field and when to use a large one. But here are some thoughts to get the ball rolling:
- Large depth of field. When might you want a large portion, or even all, of a photo to be in focus? Well, landscape shots spring to mind.
Landscape images aim to capture natural or urban scenery from the details of the foreground to the large shapes of the background. This tends to be best achieved when everything is clear and sharp.
Basically, a large depth of field suits all pictures where you want the whole scene to be clearly visible. Perhaps crowd shots or street scenes that take in a large number of people. Architectural shots that showcase every inch of a large building. Sports photos that feature the entire pitch, and so on.
Tetons and The Snake River, Grand Teton National Park, c.1942
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Problem: Understanding depth of field is tied in with understanding exposure. Having a large depth of field is not independent of the exposure for a photo. Since it requires a small aperture, admitting less light into the camera, this places demand on a slow shutter speed. In some conditions a slow shutter speed means camera shake and blurry pictures.
Solution: Use a tripod!
- Shallow depth of field. When is a narrow depth of field a good idea? Well, a narrow depth of field produces a certain intensity by isolating the subject from its background.
This can bring intimacy and emotion to portrait photos, drama to wildlife shots, precision to macro pictures or enhance the textures in still life images.
A shallow depth of field often goes hand in hand with telephoto lenses and portrait shots. When a person, or even a person's face, is the only subject of a photo it can be really effective to separate them from their surroundings with blur.
Marilyn Monroe Natural Beauty
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Problem: Well, it's not much of a problem actually, just a reminder that a wide aperture will let lots of light into the camera making it possible to overexpose the photo if you don't...
Solution: Use a fast shutter speed!
Understanding depth of field is really simple, but it will go a long way to helping you control the feel of your shots! If you have any questions about depth of field, don't hesitate to get in touch and ask me!