My Guide To Understanding Depth Of Field In Photography. Hi, and a very warm welcome to Episode 162 of the Photography Explained podcast. I’m your host Rick, and in each episode, I will try to explain one photographic thing to you in plain English, in less than 27 minutes (ish), without the irrelevant details. I’m a professionally qualified photographer based in England with a lifetime of photographic experience, which I share with you in my podcast.
Here is the answery bit
Depth of field is the amount of a photo that is acceptably sharp from front to back. Depth of field is determined by the aperture, focal length and the distance from where you are to your subject. The photographer can change the depth of field for technical or creative reasons.
OK – that was the answery bit. Nice and to the point.
You can listen to the episode here
Or carry on reading – up to you.
Right, I want to cover a few things here before I get on to the talky bit.
First off, why is it called depth of field?
Suppose it was called depth of sharpness. That would make more sense to me. Depth of field? I believe this term came from, OK, I don’t know. And I do not think that this will help us.
Now, if you look into this, you will find all sorts of complicated, technical stuff. What I tell you is what you need to know. Please keep that in mind as we go through this.
So, for depth of field, think of the depth of a photo that is sharp from the front to the back of the photo. In my head, it is depth of sharpness, not depth of field. And I am sure that someone will call me out for this, but I am okay with that!
We talk about shallow depth of field, or narrow depth of field where there is less of it, and where there is more then large depth of field, or larger depth of field.
Sharpness
Sharpness is one of those rare things in photography; it is what it is. Sharpness is sharpness. Where you focus is the sharp bit. Sharp focus is very important. When you have got everything right, you get the maximum sharpness. Now, sharpness depends on what you focus on and the aperture you use.
Do you know what I am going to do sharpness next? Yes, why not?
You want the subject matter in a composition sharp; the rest is up to you. And that is where depth of field seamlessly comes into play.
How much depth of field do I need?
Why are we interested in depth of field anyway? Why is this important? Do we need to bother about this?
Yes, we do. This is very important. Use the depth of field creatively, and you take your photos to another level.
Blurry photos are not acceptable. Photos have to be sharp. And that is the bits of the photo you want sharp, which is usually the subject matter and then whatever else you want to be sharp.
The amount of depth of field, the amount of a photo which is sharp, will also depend on the subject matter on what you are taking a photo of.
If you are taking a photo of a person, a really nice effect is to blur the background. So, to do this, you would choose a large aperture. Focus on the eyes, and make sure that the aperture is not too large that parts of the face are not sharp but large enough to blur the background. Do this, and you will have a better photo than if you did not do this. And if you use a focal length of something around 85mm, mild telephoto, you will get a more pleasing effect than you will with a wide angle focal length, for example.
At the other extreme, you photograph an expansive landscape with exciting features in the foreground, a panoramic background, and stuff in between. You will need a wide-angle focal length and a small aperture to get everything sharp. But that does not mean you have to use a small aperture for all your landscape photography, far from it. It depends on the subject matter.
And there is everything in between.
But as you will see, aperture and focal length are the main things, plus how far you are from the subject. For the person, you will be pretty close, and for the landscape photo, the foreground will be close, but the background will be miles away.
And creative use of depth of field can take your photos to another level.
How do I calculate the depth of field?
Simple. There is a formula.
DoF = u² × 2 × N × C / f²
Where
- u is the focusing distance
- N is the Aperture value
- C is the circle of confusion, and
- F is the focal length
Does that make sense to you? I hope you have all got that!
See, it’s nice and straightforward to work out.
But what is the circle of confusion?
I have no idea. None at all. I have never heard of the circle of confusion. And I don’t want to! And I have never heard of this formula before.
So let’s move on, eh? Could we find an easier way?
Let me go through the terms that apply here
Aperture
The aperture is the size of the opening in the lens. You can change this by reducing the size of the opening in the lens by changing the aperture. Small apertures and large apertures are very relevant to depth of field.
And don’t forget when we are talking about the aperture setting
- Larger aperture, larger opening, more light, smaller aperture number, and less depth of field.
- Smaller aperture, smaller opening, less light, larger aperture number and more depth of field.
Maximum aperture
With the maximum aperture, the aperture is not doing anything; the lens opening is fully open. This is the maximum aperture and the number on the lens, such as a 24-105mm F4 L lens. f/4 is the maximum aperture but is the smallest aperture value number.
The maximum aperture lets the most light in but gives you the least depth of field.
Minimum aperture
The minimum aperture is the smallest opening in the camera lens; the aperture comes into play and reduces the lens opening. But it has the largest number. You can change the aperture, or the camera will do this for you, depending on your picture-taking mode.
The minimum aperture lets the least light in but gives you the most depth of field.
Focal length
Keeping it simple, this is how I describe focal length. Let’s forget all those formulas and complicated things. This will do.
If you have a full-frame camera, a 50mm focal length gives you a view similar to what we see with our own eyes.
Now, if you change the focal length to 100mm, that is a telephoto focal length. The field of view is reduced, and things are closer.
And you get less depth of field.
If you change to a 25mm focal length, this is a wide-angle focal length, giving you a wider field of view, and things seem further away.
But you have a greater depth of field.
I have added this to my list to cover in a future episode; there is more to this but the fundamentals I have just told you.
Telephoto lenses get you closer to the subject; wide-angle lenses, not surprisingly, do the opposite. And this relates to the next point.
Distance from you to the subject
The other factor in depth of field.
The closer you are to the subject, the less depth of field there is. And the further away you are from the subject, the greater the depth of field. There you go, nice and straightforward.
Now, with a landscape photo, the main subject is both in the foreground and the background. This means you need more depth of field than when photographing a person, where the main subject is a person. Another thing that we photographers need to do is to consider the camera-subject distance and how this affects the composition. Change these, and we might change the depth of field.
And change your position, and you can change the perception of depth of field. So, the work starts with where you take the photo from.
And there’s more.
OK, those are the three main factors affecting depth of field, but this being photography, there is more to think about. Sorry.
Crop factor
This affects the effective focal length, which directly impacts the depth of field.
Depending on your camera, you might have to apply a crop factor. If you have a full frame camera, don’t worry. If you have a cropped sensor camera, you must apply a crop factor of 1.5 – 1.6, depending on your camera.
And if you have a micro four thirds camera, you must apply a crop factor of 2.
A full frame camera has a larger camera sensor size than a cropped sensor camera, which has a larger camera sensor size than a micro four thirds camera.
Check out the last episode of the podcast to learn all about this – cunningly titled What Is Crop Factor?
Does crop factor affect depth of field?
This answer has two parts: one I get and one I do not get.
The crop factor changes the effective focal length, and focal length changes the depth of field, so yes, this impacts the depth of field.
And there is the bit that I do not get – a larger sensor will have a shallower depth of field than a smaller sensor, all things being equal. Full frame cameras have larger sensors than cropped sensor cameras, which in turn have larger sensors than micro four thirds cameras. I have already said that, haven’t I? I use full frame and micro four thirds cameras, and to be honest, treat each separately; the depth of field is what it is for each camera system.
I don’t understand why, so this is what I do. I park that theory and stick to the depth of field I am getting when I use my full frame and micro four thirds cameras.
Depth of field – the good news
The depth of field, or depth of sharpness as I like to call it (have I mentioned that before?), is the depth of the sharp bits in a photo from front to back.
Depth of field varies with the aperture, focal length and what you are focussing on – the actual point of focus.
Now, I dodged this subject in the last episode for a reason. Because this can get complicated. But there is good news.
What’s the good news, Rick?
These days, to calculate the depth of field, all you need is an online depth of field calculator or an App that does the same.
Now I use Photopills. It’s a strange name, but it’s a great app. And no, I’m not being paid to tell you about this. I am a paying customer, and I use this app to help me to take photos. Sure, there are lots of other online calculators out there and lots of other great apps. This is the one that I use.
There is an app and an online depth of field calculator. And a lot more, I have to say, all helpful stuff. The app currently sells for $10.99. I couldn’t find a UK price, but it is about a tenner. And it’s well worth it.
I will add a link to the post for this episode. Here is the link to Photopills.
The online depth of field calculator asks for the following information.
- Camera
- Focal length
- Aperture
- Subject distance
(And if you have a teleconverter)
Put the numbers in, and it tells you all sorts of depth of field stuff. And also what the hyperfocal distance is.
Hyperfocal distance
The hyperfocal distance is the closest point for the aperture and focal length used, at which a lens can be focussed, where whatever is at infinity is acceptably sharp. Using this distance, everything from half that number to infinity is sharp.
The closest point where everything from that point to infinity is sharp.
So how does this work in practice?
Well, you need to bear in mind the key things
- Large aperture – less depth of field
- Small aperture – more depth of field
- Long focal length – less depth of field
- Short focal length – more depth of field
- Close to the subject – less depth of field
- Further away from the subject – more depth of field
How can I see the depth of field that I am getting?
When I started in photography, the camera lens had a depth of field scale. What you used to do was this. You used to focus on the subject, and the marks on the lens would show you the distance in front of and behind the point of focus that would be in focus.
And that was all we had. Oh no, sorry, there was also a depth of field preview button.
And my Canon 6D has one of these, a depth of field preview button. Press the button, and you can see the depth of field. The problem is that the smaller the aperture selected, the darker the viewfinder goes. I have never used this button much; it never seemed to help me.
So these days, we have another thing we can do on digital cameras: look at the photo you have taken on your LCD screen. This is a wonderful thing to be able to do, and you can zoom in on the screen to see what is sharp and what is not.
Okay, and in practice?
The first thing we need to sort with depth of field is how much of a composition we want to be sharp and how much of a composition we do not want to be sharp. That will determine everything; that is the starting point, and that is down to you, dear listener.
This will depend, of course, on what you are photographing and what you want your photo to look like.
Let the camera help you.
If you have a camera, you will probably have some automatic modes that will do this for you. On my Canon 6D, I have these two
- Portrait Mode
- Landscape Mode
There are others, but these are great examples. And I had to refer back to the camera manual for these. I mentioned this before, but the manual that comes with your camera is a great reference.
Try these modes, look at the photos, and see the camera settings used. You can try portrait and landscape mode on the same subjects and see the difference.
The camera chooses the best aperture, along with many other things, for that subject. And this is a great starting point. Nothing is wrong with these modes, especially if this stuff is new to you. They are there to help you. I will tell you what I do in a minute.
If you want to get more advanced, try AV Mode, where you select the aperture, and the camera chooses the correct shutter speed: large aperture, less depth of field, small aperture, more depth of field.
I will not give you a load of examples of the aperture, focal length, subject matter, or subject distance from the camera – there are endless examples of that online.
I want to tell you what you need to know to be able to work this out for yourself.
Here is the talky bit
I am nearly done here. I want to say this. The whole point of my podcast is to explain things so we photographers understand them. And when I was researching this episode, I came across stuff I had never heard of. I have never used that formula to calculate the depth of field and never heard of the circle of confusion. Nor another term I found – different maximum circle of confusion.
I am sure that this stuff is good and that some think we need to know this stuff, but I have managed for over 40 years, so I am OK not using this formula, and I do not need a circle of confusion; I am confused enough; thanks!
Please keep it simple: understand your camera and the settings you use and apply this knowledge to what you are taking photos of. This does not have to be a burden. You can use the tools available to get the photos that you want.
Now, I know that there is loads more stuff that I could go on about in this episode, but I don’t want to. I have told you what you need to know to get your head around depth of field and use it to take better photos. And if there is something that I have not explained, let me know, ok?
This little lot applies to all camera manufacturers, including SLR, DSLR, and mirrorless cameras.
Right – talky bit over. That was a nice short one.
What if I use a phone and not a camera?
Phones, by default, use wide-angle focal lengths, so there is already a decent amount of depth of field. And then, there are portrait modes where the depth of field is electronically changed to great effect.
Depth of field on phones is controlled using apps and settings rather than the depth of field scale.
What if I use a film camera?
All of the above applies, apart from checking the photo you have just taken on the screen on the back of your camera. The principles apply; of course they do, and you can use modern fangled apps to help you get the camera settings you need. They will all work just fine because the principles are precisely the same.
What do I do?
I use a full-frame Canon DSLR, and I also use an Olympus micro four thirds camera. I tend to use wide-angle focal lengths, and I tend to use f/8 – f/11.
With my Canon 6D and 17-40mm lens (wide angle lens), with an aperture of f/8, the hyperfocal distance is 1.22m. And the near limit changes with the subject distance. So, with that focal length and aperture, I have a vast depth of field. So much so that I will be okay if I focus, in very crude terms, a third of the way in. This is a rule of thumb that you can try if you are still figuring out what to do – see how it works for you.
So, for most of my work, I focus about a third of the way into the composition, which is me done. I know that by doing this, I will get what I want sharp. And I do this by manually selecting a single focus point once I have the composition I want.
And that is depth of field for me. This general rule of thumb works and is dead easy to understand.
I do not need to worry about depth of field when I am on a shoot because I know it is sorted. This applies to interior and exterior photos of buildings and landscape and my travel photography work.
This is what I do.
Some thoughts from the last episode
Episode 161 – Photography Explained Podcast – What Is Crop Factor?
Well, it snook into this episode earlier. Crop factor seems complicated, but I explained it OK. I have had no complaints from the last episode, which is good!
I have covered the bit that I did not cover in this episode, so it’s all good as far as I am concerned.
My one thought is this. I keep thinking about people who get into photography using their phones and wonder if they would ever be bothered about all this stuff.
After all, phones are amazing these days, and they can take amazing photos.
So why bother?
It worries me that photography will be phones and nothing else at some point in the future.
This is why I am going to revisit the episode Do I Really Need A Camera In 2022? Or Will My Phone Do Instead? And the new title will be, wait for it, Do I Really Need A Camera In 2023? Or Will My Phone Do Instead?
Next episode
Histograms. It was Histograms, but sharpness came up in this episode, and I want to cover that. Why Is Sharpness In Photography So Important?
Ask me a question.
If you have a question you would like me to answer, head over to the podcast website – photographyexplainedpodcast.com/start, where you can find out what to do. Or say hi. It would be lovely to hear from you.
And it would save me from having to come up with a question!
You don’t have to ask me a question for a podcast episode; you can just ask me a question, and I will get back to you, and it might get made into a new episode. But I will get back to you and give you a shout-out on my podcast.
That’s all
For a change, this episode was not brought to you by a cheese and pickle sandwich and salt and vinegar crisps washed down with a nice cold Diet Pepsi before I settled down in my homemade, acoustically cushioned recording emporium. No, it was two pieces of toast and a coffee! Today’s acoustic treatment is two pillows, and I have a new blind to the window. My new recording emporium is working a treat.
I’ve been Rick McEvoy; thanks again very much for listening to my small but perfectly formed podcast (it says here) and for giving me 27 ish minutes of your valuable time. I think this episode will be about 29 minutes long after I have edited out the mistakes and other bad stuff.
Take care, stay safe.
Cheers from me, Rick
OK – that was the podcast episode.
Want to know more?
Head over to the Start page on the Photography Explained Podcast website to find out more.
And here is the list of episodes published to date – you can listen to any episode straight from this page which is nice.
Let me know if there is a photography thing that you want me to explain and I will add it to my list. Just head over to the This is my list of things to explain page of this website to see what is on there already.
Let me send you stuff
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And finally a little bit about me
Finally, yes this paragraph is all about me – check out my Rick McEvoy Photography website to find out more about me and my architectural, construction, real estate and travel photography work. I also write about general photography stuff, all in plain English without the irrelevant detail.
Thank you
Thanks for listening to my podcast (if you did) and reading this blog post (which I assume you have done as you are reading this).
Cheers from me Rick
