Look at a portrait where the person is sharp and the background melts into a soft blur. Then look at a landscape where everything, from the flowers at your feet to the far mountains, is sharp. The difference is depth of field. You already know that aperture affects it. In this lesson you will learn exactly what depth of field is, all the things that control it, and how to use it to make your subject stand out.
What is depth of field?
Depth of field is the zone of a photo, from near to far, that looks acceptably sharp. In front of and behind that zone, things gradually become softer.
Remember the plane of focus from what is focus: only one distance is perfectly sharp. But things a little in front of it and a little behind it are only slightly blurred, so little that our eyes still see them as sharp. That range of "sharp enough" is the depth of field.
| Term | Meaning | Looks like |
|---|---|---|
| Shallow depth of field | Only a thin zone is sharp | Sharp subject, very blurred background and foreground |
| Deep depth of field | A large zone is sharp | Most of the scene is sharp from front to back |
Why "acceptably" sharp?
Outside the plane of focus, each point of light spreads into a tiny blurry circle. Photographers call it the circle of confusion. While those circles are very small, our eyes cannot tell them from sharp points. Once they grow large enough to see, the area looks blurred. This is why depth of field also depends on how big the photo is viewed: a small phone image hides blur that a large print would show.
The factors that control depth of field
| Factor | Shallower depth of field | Deeper depth of field | Learn more |
|---|---|---|---|
| Aperture | Wider aperture (small f-number, e.g. f/1.8) | Narrower aperture (large f-number, e.g. f/11) | aperture |
| Focus distance | Focusing close to the camera | Focusing far from the camera | This lesson |
| Focal length (from the same position) | Zooming in / longer lens | Zooming out / wider lens | focal length and angle of view |
| Sensor size (same framing and f-number) | Larger sensor | Smaller sensor | sensor formats |
Remember:Phones have very small sensors and very short lenses, which is why their normal photos have deep depth of field. Their "portrait mode" blur is mostly created by software, not by the lens.
Focus distance: the most underrated factor
Beginners usually think only about aperture. But distance has a very strong effect. When you focus very close, depth of field becomes extremely thin, even at a medium aperture. When you focus far away, it becomes much deeper.
- A flower photographed from 30 cm at f/5.6 may have only a few millimetres sharp.
- A building photographed from 50 m at f/5.6 may be sharp from front to back, with the background too.
This is why close-up and macro photos struggle to get enough depth of field, a challenge covered in depth of field at high magnification.
Where the sharp zone falls
Depth of field is usually not equal in front of and behind your focus point. At normal distances, more of the sharp zone falls behind the focus point than in front. A common rule of thumb says about one-third in front and two-thirds behind. This is only an approximation: when you focus very close, the split becomes nearly equal, and when you focus far away, much more falls behind.
Tip:For a group photo with two rows of people, focus on the front row's eyes or slightly behind them, not on the back row. Since more depth of field falls behind the focus point, both rows have a better chance of being sharp.
Subject separation
Subject separation means making your subject stand out from its background. Shallow depth of field is one of the strongest ways to do it: a sharp subject against a soft background immediately catches the eye.
But aperture is only one part. The distance between your subject and the background matters just as much. If a person stands right against a wall, the wall is almost at the same distance, so it stays fairly sharp even at f/1.8. Ask them to step 3 metres away from the wall, and the wall becomes much softer with the same settings.
| What you change | Effect |
|---|---|
| Open the aperture wider | Shallower depth of field |
| Move closer to your subject | Shallower depth of field |
| Move the subject further from the background | Background falls further outside the sharp zone |
| Use a longer focal length and step back | The background looks larger and more blurred |
Blur is not the only way to separate a subject. Light and color can do it too: a brightly lit subject against a darker background, or a red coat against green trees. You will learn these in background lighting and subject separation and color, contrast and visual emphasis.
Common mistakes
- Relying only on aperture: subject-to-background distance often matters more for blur.
- Standing people against walls for blurry backgrounds: the wall is too close to blur.
- Forgetting that close-ups have very shallow depth of field: even f/8 may not be enough.
- Focusing on the back row of a group: the front row often falls out of the sharp zone.
How professionals control depth of field
Professionals control depth of field with all the factors together, not just the f-number. A portrait photographer chooses a background far behind the subject, moves close, and uses a wide aperture. A product photographer shooting close up stops down and checks that the whole product is sharp. A landscape photographer chooses a moderate aperture and a careful focus point to keep near and far sharp, which you will learn in the next lesson.
Practical examples
A portrait against a busy street
- Situation
- At f/2.8, the shops behind your friend are still distracting.
- What to do
- You ask your friend to walk 10 metres away from the shops, step closer yourself, and keep f/2.8.
- Why it works
- More distance between subject and background, and a closer focus distance, both make the background softer.
- Result
- The street becomes a smooth, colorful blur behind a sharp face.
A family in two rows
- Situation
- At f/4, the back row is sharp but the front row is soft.
- What to do
- You focus on the front row and change to f/8.
- Why it works
- Depth of field extends further behind the focus point, and a narrower aperture deepens it.
- Result
- Both rows are sharp.
Key points
- Depth of field is the zone from near to far that looks acceptably sharp.
- Aperture, focus distance, focal length and sensor size all affect it.
- Focusing closer makes depth of field much shallower.
- At normal distances, more of the sharp zone falls behind the focus point than in front.
- For subject separation, increase the distance between subject and background, not just the aperture.
Frequently asked questions
What is depth of field?
What affects depth of field?
How do I get a blurry background?
Is depth of field split one-third in front, two-thirds behind?
Conclusion
Depth of field is controlled by aperture, distance, focal length and sensor size working together. Use them to keep everything sharp or to isolate your subject, and remember that the space between subject and background is one of your strongest tools. Next, you will learn when to choose shallow or deep depth of field, and how to get the most sharpness in a landscape.
Finished reading? Track your progress through Focus and depth of field.