When you think about controlling the depth of field, the aperture may instantly come to mind. In its simplest form, this would be correct. However, other factors are at play regarding depth of field. Knowing these different factors will help you understand and control your depth of field.
Manipulating the factors of aperture, distance to subject, and focal length and how they affect depth of field will allow you to master this critical skill of creating stunning images, whether portraits or landscapes.
What is Depth of Field?
First, you must understand depth of field. In its simplest form, depth of field is the distance between the nearest and furthest objects that appear acceptably sharp in the image. Easy, right?
Aperture Versus F-Stop
Suppose you have ever talked to another photographer or anyone remotely interested in photography. In that case, you will hear them talk about aperture and f-stop and, more than likely, interchange the two during a conversation. I also fall into this trap when explaining depth of field and that there is a difference. What's the difference?
The aperture is the adjustable opening in a lens, and its size is measured by the f-stop number. Now that we know the difference between aperture and f-stop, we can explore what you can achieve with various f-stops. Knowing that the f-stop is the size of our lens's aperture will help us better understand the difference between a shallow depth of field and a deep depth of field.
Shallow Depth of Field Versus Deep Depth of Field.
You may have heard the terms shallow depth of field and deep depth of field. What do they mean, and how do we achieve these results? A shallow depth of field has a blurry background, and a deep depth of field has everything in focus, from the foreground to the background of your image.
Achieving a Shallow Depth of Field and Deep Depth of Field
Everyone wants a nice out-of-focus background in a portrait or macro image. To achieve these results, you will need a lens with a small f-stop (large opening) between f/1.4 and f/5.6. Using a small f-stop number will do two things. First, you will achieve that blurry background or bokeh in your image, separating your subject from the background. Second, it will allow more light to pass through your lens onto your camera's sensor. We constantly strive for a shallow depth of field and forget about trying to achieve a deep depth of field in our image. You will choose an F-stop of f/5.6 or greater, allowing for a greater depth of field(small opening) and achieving more of your image in focus. Usually, you would choose a deep depth of field for a landscape image or where you want more of the background in focus.
Accurate Focusing
Achieving an accurate focus is critical when it comes to depth of field. When focusing, you will want to focus on your subject. This will ensure that your subject is in focus, and your choice of f-stop will determine how much of your subject is in focus.
Subject Distance to Camera
The closer your subject is to your camera, the shallower the depth of field will be. If you back off your camera from your subject, you will get a deeper depth of depth in the field. When leaving your aperture the same, this will still occur. I have been asked why their background is not blurry, but I use an aperture of f/2.8. The first question I ask is, “How far was your subject from the background?” The usual reply is, “Only a few feet.” Another thing to remember is that the closer your subject is to the background, the less your background will be blurred. I prefer to have the subject at a minimum of 6 feet from my background for a portrait, if possible.
Lens Focal Length
Even the focal length of your lens will affect your depth of field. If you choose a 200mm lens, you can get some serious bokeh (blur) action. When photographing portraits, I love to use my 70-200 f/2.8 to produce a shallow depth of field. If we jump to the other end and choose a focal length of 14mm on a wide-angle lens, this will make an image that is sharp from foreground to background, even with an aperture of f/3.5. You would likely need an aperture of f/16 to achieve the same depth of field.
Sometimes, I am in the field, and I would prefer an extremely shallow depth of field for a flower. I will use my Nikkor Z 70-200mm f/2.8, use a focal length of the lens at 200mm, and then get as close as my lens will focus, or its minimum focusing distance (3.28 ft). This will allow me to achieve an extremely shallow depth of field because I moved close to my subject and used a focal length of 200mm.
Choosing the Right F-Stop
I often get the question, “What aperture do I need?” I always respond with, It depends. The first thing I think of is what I want to achieve in the photograph I am creating. Here are a few things I take into consideration when choosing your f-stop.
Subject
Consider your subject. If you create a portrait, you can use a lower f-stop (e.g., f/1.8) to give a nice bokeh in the background. This will separate your subject from the background. If you're a natural light photographer, you may have your subject in a preferred lighting scenario. The background in that location might not be great, so you can blur the background to make a distracting background more aesthetic. It will also allow your subject to stand out! If you are shooting a landscape, you may want to use a larger f-stop (e.g., f/16) to increase your depth of field. This will give more focus from the foreground to the background.
Light
Occasionally, you may be in a situation where the light is low, and need more light to enter your lens. This will allow you to gain a faster shutter speed when combined with ISO. On the other hand, the image may be too bright (overexposed), and using an f-stop like f/16 reduces the amount of light entering the camera.
Creative Effect
There is no right or wrong answer when choosing an aperture. Are there best choices? Yes! You have heard the old saying, think outside of the box. I tell students to think like there is no box. This is because if our box is still there, we tend to go back to the box, restricting our thought process on keeping an open mind. This will allow us to go back to our old ways! Experiment and see what combinations of different f-stops can do for your photograph!
Conclusion
In the end, knowing the depth of field is affected by more than just the aperture in your lens. When you know the focal length, the distance to the subject also plays a big role in the result of your image. You can start making educated decisions in image-making, resulting in less frustration. When you know how to diagnose the problem, you know how to fix it. Depth of field doesn’t have to be a challenging issue, and in the end, if you keep a few things in mind, depth of field will be another thing you can quickly master!
Focusing distance plays a huge role and many times I still shoot wide open when focusing at near infinity because it achieves the same effect without 1) slow me down changing my settings and 2) can allow for faster shutter speeds especially when using a long lens.
Of course sometimes in situations where achieving accurate focus where my subject is moving quickly, I'll sometimes stop down just to guarantee "focus" through increased depth of field.
Yes! I feel like like this is where people tend to forget and get burned. 😆
I guess you could say Bob Ross painted with perfect depth of field. The trees were always happy.
Love it!
When trying to explain this to others, I have found having an older lens with a graduated focus ring and the colour markers to show DOF for various f-stop values is very helpful. The closer distances are further apart on the focus ring and the further distances get closer together until infinity, showing how the subject to camera distance can affect DOF. The colour markers help explain hyperlocal distances or just simply what aperture will focus the desired elements of your view.
All of those lens markings assume a non-cropped image enlarged to standard display size (8x10 or 8x12), standard viewing distance (10-12 inches), by a person with 20/20 vision. Change any one of those factors and the lens barrel markings go out the window. For instance, if we plan to print a 24x16 image to be viewed at 12 inches, the DoF will be roughly half of what is indicated on the lens barrel.
laughing at your Bob Ross Figurine because we have the same one at work. He is a cherished mascot. Someone even knit him a little scarf. Glad to see Bob is helping with photography lessons.
That's awesome!
Another "focal length matters" article, aren't we past these yet? Focal length affects how the DoF is distributed in front/behind of the subject given the same field of view, but that's it, it does not affect the amount of DoF.
It seems the author assumes you can't move your body and it's true that if stand in the same spot and change lens, the DoF will change, but it's important to understand why, it's not the focal length itself but the subject size / field of view that causes this (in relation to the sensor size).
Sensor size and aperture, those two are the only relevant variables for understanding DoF given a specific field of view.
Thanks, I was going to write in more depth and detail but wanted to keep things shorter!
Both focal length and subject distance are factors, among others, that determine total magnification. The only two things that matter for DoF are aperture and total magnification.
The one point not mentioned is Focus Mode wide, zone, center fixed, tracking: center fixed, Tracking: Center Fixed or Spot L and subject AF. They all intermix. As well as all you mentioned.
Is your head spinning if not go to a YouTube site that it is explained some or buy the 600 page book on your new modern camera and go page by page till it is. Now make a cheat card big it will be!
Next is it day or night? Just for info night is not affected as much because somehow at night you get from right in front of camera to horizon you get perfect focus, buildings on horizon with windows you can zoom in on and see a TV is on or a building with all rooms with big windows everything in each room perfect looking.
But also MF with the colors (red, white, yellow) to show where focus is close or far. What to chose? Then waiting for the the green light to come on saying all things chosen are good to go!
Just thought I would toss all that in also!
Thanks! I was going to write more but it was a little long. Thank you for the feed back.
Holga is on my list! I love medium format, back in the day I used a Hasselblad in school!
"The aperture is the adjustable opening in a lens, and its size is measured by the f-stop number. Now that we know the difference between aperture and f-stop..."
No, the aperture is the diameter of the smallest opening passing through the lens, as measured through the front element, (which, generally being a positive element, magnifies the size of the opening). The f/stop is a fraction: the focal length of the lens divided by the aperture diameter. A 50mm lens with a 25mm aperture is f/2. 50/25=2. A 100mm lens with a 25mm aperture is f/4. 100/25=4.
"The closer your subject is to your camera, the shallower the depth of field will be. If you back off your camera from your subject, you will get a deeper depth of depth in the field."
Correct. But...
"Even the focal length of your lens will affect your depth of field. If you choose a 200mm lens, you can get some serious bokeh (blur) action. When photographing portraits, I love to use my 70-200 f/2.8 to produce a shallow depth of field."
As the previous section had just pointed out, increased distance from camera to subject increases depth of field, and the longer lens means backing off from the subject to keep the same subject size in the frame. Staying away from ultra-wide angles (which are generally not used for portraiture), depth of field is often shallower with the sorter lens because you are closer.
And while it's nice you can afford a $2700 fast constant-aperture lens, most photographers don't have that. Less-expensive zooms, like the lenses that come with the camera, lose an f/stop or more when you extend the focal length, increasing depth of field.
Technically, the size of the aperture opening as it is viewed through the front of the lens is called the "entrance pupil". Likewise, the size of the aperture as viewed from behind the lens is known as the "exit pupil". The actual size of the aperture is the physical size of the aperture. F-number is calculated by dividing focal length by *entrance pupil* diameter.
If you're going to get pedantic about it, please get it right
"Technically, the size of the aperture opening as it is viewed through the front of the lens is called the 'entrance pupil'... If you're going to get pedantic about it, please get it right "
I wrote: "No, the aperture is the diameter of the smallest opening passing through the lens, as measured through the front element..." I did get it right. If you're going to correct someone, read what they said first. Duh.
What you describe is the *entrance pupil*, not the aperture.
As I said, the aperture is measured THROUGH the front of the lens. The front of the lens is the entrance pupil.
Go back and read my original statement again: "the aperture is the diameter of the smallest opening passing through the lens, as measured through the front element, (which, generally being a positive element, magnifies the size of the opening)."
The front element is the entrance pupil. The entrance pupil is the front element. The aperture is the diameter of the opening in the lens as measured through the front element, also known as the entrance pupil.
"The *entrance pupil* is the diameter of the smallest opening passing through the lens, as measured through the front element..."
There, I fixed it for you. Not to mention that almost all wide angle lenses have negative elements between the front of the lens and aperture diaphragm. Any retrofocus design reduces the size of the e.p. compared to the actual physical size of the diaphragm.
Only two things affect depth of field: total magnification and aperture. The factors that affect total magnification include subject distance, focal length, enlargement factor/display size, and viewing distance.
You can take the same exact photo, display them at two different sizes viewed from the same distance and they will have different depths of field. Likewise, you can view the same exact photo at a given display size at two different distances and the DoF will change.
Depth of Field is an illusion. Only one distance from the camera is in sharpest focus, everything else is blurrier to one degree or another.
It's the points on either side of the focus distance where our eyes can just begin to perceive blur that we usually define as "acceptably sharp".
"Depth of Field is an illusion. Only one distance from the camera is in sharpest focus, everything else is blurrier to one degree or another."
All of photography is an illusion. But if you want to get all technical, "sharpest focus" is just the smallest circle of confusion a lens will focus. Some lenses focus smaller circles of confusion than others, though none are perfect points. "Acceptably sharp" is a small enough circle of confusion to be satisfactory to the photographer. Your "acceptably sharp" may be different than mine, and if I'm working with a deliberately shallow depth of field or in a pictorialist mode, the question is moot.
Is this image, from an 8x10 contact salt print made with an Imagon lens, "acceptably sharp"?
Thus the word "usually". If you want your images to look like you had Vaseline smeared all over a piece of pantyhose stretched over the front of your lens, that's your prerogative.
The "smallest circle of confusion" is just another way of saying "most in focus" or "in sharpest focus". The fact remains, there's only a single distance along any axis from the imaging plane to the scene that has the smallest circle of confusion. Everything closer and further has a larger CoC.
Photography is not an accurate representation of "reality", whatever that is, but when one views a photograph one is looking at an actual photograph, not an illusion of a photograph. The photograph doesn't disappear if one examines it closely enough. Within that photograph any perceived DoF *is* an illusion. Under close enough scrutiny, the DoG gets narrower and narrower until it is gone.