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Understanding depth of field featured image.

The depth of field (DoF) is one of the key factors that change the look, feel, intention and even emotions in your photograph.

It allows you to draw attention and lead your viewer’s eye to a certain element in your photo.

Or you can you use it to showcase an awesome landscape and immerse your viewers into the scene.

Heck, it can even be the difference between a sharp and blurry image.

We introduced this term on our article about aperture. The goal here is to expand on that and to get a deeper understanding about Depth of Field.

What is Depth of Field?

Simply put, it is the “plane” of acceptably sharp elements in your image that are perceived as in-focus.

Let me expand on this.

Your camera can only focus at its sharpest on one plane of the scene you’re trying to capture.

From that point of focus, the image will transition from sharp to unsharp as the distance from the focus point increases on both front and back.

What is depth of field.

However, the transition from the sharpest (in focus) elements to the unsharp ones (out of focus) is very gradual.

Most of us perceive some parts of the image as sharp even though it isn’t as sharp as the actual point of focus.

Depth of field is the part of an image that we perceive as in-focus and sharp.

The plane of acceptable sharpness will shrink or expand depending on a few factors. More on this later.

Shallow vs Deep Depth of Field:

Shallow vs Deep Depth of Field

Shallow Depth of field refers to an image with a very small amount of in-focus elements. It creates background blur and a sense of separation between your subject on your background.

It is often used in macro, wildlife and portrait photography. And help you direct your viewer’s attention to what is important in your image.

Shallow depth of field example
Shallow Depth of Field example.

Deep Depth of field, on the other hand, have a very large amount of in-focus elements. It kind of sucks your viewers into the scene. Often used in landscape and architectural photography.

Deep depth of field example.
Deep depth of field example.

How the depth of field is perceived:

The degree of acceptable sharpness we perceive is not always the same. And it can vary based on a few things:

  • Enlargement – If you are printing your photos, it depends on how large your actual print size. Will you enlarge the original photo’s size to a billboard size? Or do you just need a pocket size image?

    This isn’t exclusive to physical prints.

    As you know, web images have dimensions too. Changing the dimensions will affect the overall sharpness of your image.

    Some elements that don’t look unsharp in its original size may even start to lose its sharpness if you blow up your image too much.

    For example, your camera captured a resolution of 1920×1080 pixels. If you blow it up to billboard size, then you might not have a very sharp image.

  • Viewing Distance-  Will it be viewed at a distance like how billboards are usually placed? Or will it be viewed at a close distance like from your chair to the monitor?

    As we get closer to the image we are viewing, the lesser depth of field we can perceive.

    For example, if we view a billboard-sized image at a close distance, we’ll probably see a lot of unsharp details in the image.

    But if we view it on a far distance, the unsharp portion that you saw at a close distance will not be noticeable.

  • Viewer’s visual acuity – The “blur tolerance” varies from person to person. A person with 20/20 vision will perceive sharpness differently from a person that has, say 6/6 (normal) vision.

    When it comes to the perceived depth of field, a person with better eyesight will have lesser “blur tolerance” compared to those with poorer eyesight.

    Provided they are looking at the same image enlargement at the same comfortable distance.

In short, a portion of your image that looks sharp and in-focus may look quite unsharp based on the enlargement from the original size, the person’s visual acuity and the distance of that person from the image.

The factors we mentioned here are actually parameters on calculating the circle of confusion.

If you want to understand the technicalities and more information about how the depth of field is perceived, check out our in-depth article about the Circle of Confusion.

Practical ways to control the Depth of Field:

The depth of field is mainly affected by aperture and subject magnification.

If you’ve read our beginner’s article about f-stops, I’m sure you are already familiar with aperture. The new term here is the magnification.

Magnification describes how big or small a certain object is projected in your camera sensor. You can increase it by either moving closer to your subject or by using longer focal length.

There are other factors that can indirectly shift the DoF. But as you probably notice, photography can get a little geeky sometimes because it involves a lot of physics.

So instead of bombarding you with a lot of complicated concepts, here’s a list of actionable ways to control the perceived depth of field:

  • Change the aperture.
  • Change the focal length.
  • Change the physical distance between the subject and camera sensor.
  • Change the distance of the subject from the background.
  • Use a different camera with different sensor size.
  • Focusing on the hyperfocal distance.

Let’s have a closer look at each, shall we?

Aperture:

Changing your f-stop settings directly affects the depth of field. This is due to the fact that changing the aperture size also changes the light’s path to the camera sensor.

When you use a wider aperture (lower f-number), the depth of field shrinks. It results in a lesser amount of acceptably sharp “plane” in your image.

While if you use a higher f-number, the DoF expands. This results in more portion in your image that will have acceptable sharpness.

Aperture affects the depth of field.
Larger aperture decreases the depth of field.

Using a very wide aperture like f 2.8 or lower will render a very shallow depth of field. You often see these images on macro, wildlife, portrait and sports photography.

Landscape and architectural photographers, on the other hand, often loves taking an image where all or almost all objects are in focus. They want to have a very Deep Depth of Field almost exclusively.

As you can guess, it is usually achieved by using a smaller aperture.

Subject’s distance from the camera: (Focus Distance)

It’s pretty straightforward.

You will get a lesser amount depth of field as you move closer to your subject.

Similarly, if you move the subject farther from your camera, you will have a deeper depth of field even if you use the same aperture value.

Let’s see it in action:

Depth of Field and Focus Distance.

You notice right away that it looks a lot different. Aside from the background blur, the subject looks bigger. Not to mention, the objects in the background seems to have been spaced differently.

This sense of depth and spacing is called perspective.

When you physically move away or closer to your subject, you are also changing the perspective of your image.

This change in perspective is the main difference between moving with your feet versus just changing the focal length of your lens. We’ll get into that shortly.

First, there’s just one thing we should keep in mind…

As far as your camera is concerned, the subject is anything that is in front of your lens. So technically, the background is still part of the subject.

There are some cases where you need to create enough background blur but you can’t increase your f-stop or move any closer for the sake of proper framing.

What you can do, is increase the distance of your subject from the background.

By doing so, you can create a blurrier background.

This doesn’t actually change the amount of depth of field. It just increases the distance of the background from your focus point.

Remember, the further an object from the focus point, the less sharp it will be.

Focal Length:

When you got your first camera, you probably bought the zoom kit-lens along with it. These zoom lenses let you use different focal lengths in a single lens.

If you played around with it, you know that if you increase the focal length, you get that more “zoomed” look as though you have physically moved closer.

However, there’s a slight difference…

Longer focal lengths only magnify the image the same way a magnifying glass does. It does not affect perspective as opposed to physically moving closer to your subject.

Instead, changing focal lengths affects the field of view(FoV).

FoV is what your camera can capture in the actual scene once the light passed through the lens.

When you use longer focal length (higher mm number), your camera “sees” less of the actual scene. At the same time, your subject will also look bigger. (narrower field of view and higher magnification).

While if you use a shorter one(lower mm number), your camera will be able to see more of the scene. And the subject appears smaller.

Focal Length and Field of View

This is true whether you are using a zoom lens or changing from different prime lenses.

So how does it relate to the depth of field?

Using longer focal lengths will reduce the depth of field. This is assuming that you stay at the same distance from your subject and keep the aperture and everything else the same.

However…

You can essentially get almost the same depth of field regardless of the focal length. This is done by physically moving backward or forward while maintaining the subject’s magnification in the frame.

Matt Granger demonstrated this in this video:

But since you changed your physical distance, the perspective is also changed. So even if you achieved the same amount of background blur, the image is still essentially not the same.

This technique of getting the same amount of blur by physically moving doesn’t apply with extreme telephoto lenses, say a 16mm vs 400mm or above.

Here’s a little tip: If you’re just starting out, I would suggest to always “zoom with your feet” whenever you can. This will force you to get creative with your shots.

Sensor Size:

Sensor size does NOT affect the amount of depth of field that much. That’s because the sensor size does not affect your image the same way as focal length or physical distance.

Basically, it just crops parts of the image that you would otherwise get on a bigger sensor.

You will essentially have the same amount of depth of field regardless of your sensor size. This is assuming you are using the same exact lens at the same exact settings and distance.

So a 50mm lens mounted on a full frame lens will pretty much have the same depth of field if this same lens is mounted on an APS-C camera. The only difference is the perceived field of view.

This is called crop factor.

Case in point, here are two images were taken with the same lens, camera settings and distance from the subject. The only thing that changed is the camera body.

Crop factor and depth of field.

The image shot with the full frame body has more elements in the frame. While an image shot on the APS-C camera has fewer elements, creating a “zoomed-in” look.

But do you see any huge differences in the amount of blur in the background? If there is, it is probably not that much.

Imagine putting a cookie of exactly the same size at different plate sizes. One looks bigger than the other no?

It’s like an illusion. You think that you are getting a more zoomed look and more depth of field. When in reality, your smaller sensor only captured a portion of the image that you would otherwise get on a camera with a bigger sensor.

Nothing really changed, just the cropping of the image.

So how does sensor size indirectly affect the depth of field?

If you want to get the same field of view of the full frame sensor on a smaller sensor, you will have to step back or maybe change the focal length.

Both options will change your depth of field.

Hence this is where you will get an advantage in terms of DoF when using cameras with a bigger sensor.

Does this mean it’s easier to achieve a shallower depth of field with full frame sensors?

Yes.

Does this mean that it’s better to use full frame sensors?

Nope, not necessarily. Each sensor sizes have advantages and disadvantages. But that is a discussion for a different article.

Diffraction and Depth of Field:

It’s tempting to just close down your aperture to the max just to get the deepest depth of field possible.

Take note though that there are a few limitations that you need to consider to capture a good image where everything is sharp.

One is exposure. Remember, if you close down your aperture you are reducing the amount of light passing through your sensor. This results in a darker image.

There’s really no point in getting the maximum depth of field if you can’t see the actual image. Exposure triangle should always be at the back of your mind whatever type of image you are trying to capture, landscape or not.

Another limitation is diffraction. While it’s true that using a smaller aperture gives you a larger area of in-focus elements, using too small might produce a “soft image”.

Very small apertures like f/16 or higher cause blur and reduces the sharpness of the image. That’s because light rays begin to disperse and hitting other photosites that it shouldn’ have at these f-stops.

Lens diffraction and sweet spot comparison.
Comparison between the sweet spot and the smallest aperture of Canon 24-105L Lens.

Things like fungus, dirt, oil and poor lens build (from cheap lenses) can also cause diffraction.

To be honest, I don’t concern myself on this too much. The great thing about digital photography is that you can fix many things during post-processing, and diffraction is one of them.

I’d be creating a post to show you some ways to deal with it. Make sure to
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Anyway, it’s just good to know that it is there and it actually does exist and it does happen. It is always a good thing if you do not have to deal with it later in post-production. So try not to use too small of an aperture if you can.

Usually, f-stop settings of f11 and above might be susceptible to diffraction but this varies depending on the lens you are using.

And you know what? There is a better way to achieve greater depth of field than using an extremely small aperture…

Introduction to Hyperfocal Distance:

Hyperfocal distance is the distance where you can set the focus and get the largest depth of field possible. We dedicated an article on how exactly you can use it to your advantage.

For now, let me briefly describe it.

First off, everything from half your hyperfocal distance until infinity will be sharp.

Secondly, It depends solely on your aperture, focal length and sensor size of your camera. It doesn’t matter where your focus point is currently at, the hyperfocal distance will always be at a fixed distance.

There are a lot of hyperfocal distance calculator and charts that you can use and get an idea where you should be placing your focus. However, I personally do not use them because they aren’t always practical.

Plus, it doesn’t take into consideration the nearest foreground element in the scene you are trying to capture.

My favorite trick is to double the distance of your nearest foreground. For example, if your nearest foreground is at around 3 feet, set your focus at 6 feet.

Now everything from half that all the way to the background will be sharp.

Note that this trick is still more of guesswork and there are a lot of ways to go about it. I highly recommend reading our in-depth article about hyperfocal distance.

Bokeh:

Bokeh originated from the Japanese word “ボケ” pronounced as bo-ke which means blur or haze.

While that is the case, it doesn’t refer to the amount of blur of your image. It refers to the quality of the blur.

You can certainly relate the shallow depth of field with bokeh. But simply creating an image with an extremely blurred background doesn’t mean an awesome and creamy bokeh.

The quality of the blur is subjective. Some will attribute it to the number of aperture blades, some to the sensor sizes and some will attribute to the lens’ construction.

The truth is, it’s a little bit more complicated than that.

For now, here are some factors to consider for creating nice bokeh:

  • Focal length
  • Aperture(f-stop number)
  • The camera-to-subject distance
  • Distance to the background or the foreground
  • Shapes and patterns of the objects in the frame
  • Aperture iris shape
  • Foreground/background brightness
  • Colour

Depending on the sensor sizes, you may have to adjust several things listed above quite differently in order to get the look you are going for.

Image with Bokeh.

For example: If you are using a micro four-thirds camera, you might have to move further away to get the proper framing than you would on a full frame camera.

By now, you understand that by doing that you are increasing depth field right?

Well then, how about moving your subject away from the background elements then composing your frame once again?

This will give you a shallower depth of field and more control on the bokeh.

Actionable tips to apply what you learned in the real world:

You’re awesome for making it this far! All that’s left is to apply all these knowledge we gain in the real world.

How to achieve deep depth of field:

  • Use a narrower aperture(high f-stop number).
  • But avoid using too small of an aperture to avoid diffraction.
  • Move farther away from your subject.
  • Apply your knowledge about the hyperfocal length to get sharp objects throughout your frame.
  • Use wider focal length (lower mm numbers).

How to achieve shallow depth of field:

  • Use wider aperture(low f-stop number).
  • Move closer to your subject.
  • Use longer focal length.
  • Create blurrier backgrounds by moving your subject away from the background.
Depth of Field Infographics

Conclusion:

The depth of field is one of the most expressive tools you can use in photography.

While there are quite a lot of factors to look out for, they are not overly complex. A deep understanding of the depth of field and the factors that affect it can greatly improve your composition.

Hopefully, this article helped to boost your confidence in creating beautiful photos.

And don’t ever forget that as technical as photography can be, it is at its core, a form of art. So don’t get too hung up on the technicalities and have fun with photography.

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