Understanding depth of field can be made complicated. This post will give you a simple explanation, show you a few good photographic examples and give you access to several other articles if you want a deeper understanding.
This article is an brief introduction to this important topic with several resources at the end to more detailed information on how you can control it to improve your photography. This photography term is often abbreviated as DOF.
Understanding and having some control over this one important aspect of digital photography will catapult your photography abilities above many other photographers. Seriously, No BS!
Controlling the amount of DOF puts YOU in the driver's seat in emphasizing certain parts of your photograph.
The only difference in the two photos below is the size of the range of things in sharp focus. You can see size really does matter. (:-O) The only change that was made between the two photographs was the aperture or f-stop number setting on the camera.
Changing the f-stop is the most well known and easiest way to control your DOF. I focused directly on the close-up bottle in both photos. In the photograph on the left an aperture of f/4 was used. Only the close-up beer bottle is sharp and clearly in focus.
In the photograph on the right, the f-stop was f-22, the smallest opening that my lens can achieve. This increased the range of sharpness. However, there are others ways to control DOF that you will want to understand to improve your level of expertise. These include the distance of your subject from the camera and the focal length of the lens.
Because the distance of the close-up bottle to the camera was very close, even f-22 was not small enough for the farther-away beer bottle to be completely sharp.
Subject Distance. The closer the subject is to the camera then the smaller the range of things in sharp focus. So, when you do close up or macro photography, the DOF is extremely small.
Understanding DOF is extremely important when considering your photo's composition.
Just knowing how to control it's range or it's size will help you improve your photography dramatically.
You can edit photos after taking them and create blur in the background with software. That can be time-consuming. Or, you can cheat a little and use also a DOF controlling lens.
Conversely when you are photographing things that are distant from the camera, you will have more of a large range of things in focus or a deep DOF.
In this very interesting photo of Newhaven Harbor, the closest object in the photo is not real close to the camera. The Depth of Field is greater because of the longer distance of the camera to the water line.
Focal Length. The larger the focal length, then the smaller the range of things in sharp focus. So when you use a powerful zoom lens or long telephoto lens, you get a smaller or narrower DOF.
Sensor size. Another important element that many photographers fail to think about is the size of the sensor. Cameras with smaller sensors are built with small lenses and therefore have relatively larger Depth of Field compared to a camera with a large or full-sized sensor.
This is a limitation when the photographer wants to use selective focusing to emphasize only a certain area of the overall photograph.
This is a really big deal when you have a camera with a small sensor, such as a cell phone camera or a point and shoot camera. Then it is very difficult or impossible to take advantage of using a narrow depth of field to emphasize your subject. This is why professional photographers like cameras with full-sized sensors, they can achieve a shallow DOF.
There are many situations where it is often definitely desirable to have a small DOF. This is especially true when taking portraits and we are trying to intentionally blur the background.
This portrait of this high school basketball player uses a shallow depth of field to blur the background. I used a long telephoto, zoomed to 200mm and set the aperture to f 2.8 to minimize the depth of field.
This portrait was taken with a Canon 5D which has a full-sized sensor and is another factor in how much of a range is in focus.
As already mentioned, cameras with smaller sensors will produce photos that have a larger DOF. Cell Phone camera sensors are quite small so that almost everything is in sharp focus unless you have blur from motion. Lenses that can "open up" to a wide aperture have the option of getting a very shallow DOF.
With landscape photography, compositions often include objects that are close to and far away from the camera. This is a situation were a deep depth of field is desirable to keep everything in focus.
The other skill that is useful to develop is knowing exactly where to focus your lens when composing your photograph to get everything in your camera frame sharp.
What is Depth of Field? Read these several different definitions to give you a few unique ways to understand it's definition. Also why it is so important to consider when taking a photograph and a specific side by side demonstration with 3 different focus points.
Photo examples of different DOF. This article has several photo examples on the proper use of DOF to improve your photos. The photos are critiqued on how the lighting and composition are also considered when determining your camera settings.
Shallow DOF Examples. This page has a few more sample photos that show the importance of paying attention to Depth of Field.
Gallery of Deep DOF Photos. Large or deep DOF is often desirable in landscape photography. This page has a few more sample photos and corresponding critiques.
Comparison of subjects using both narrow and deep DOF. This post has diagrams showing 4 different shooting situations and how they affect the range of what's in sharp focus. Once you start paying attention to DOF, it becomes another factor that separates your photography from photos taken by the average beginning photographer.
There is a very uniquely designed lens, called the Lensbaby which has become very popular with professional portrait and wedding photographers. With it you can purposefully blur sections of your photograph to emphasize your subject without having to have a wide-open aperture.
Essentially it is a very affordable "tilt-lens" with many options available. I found this video on YouTube and it is excellent explanation of the lensbaby, how it works and how it affects the sharpness in areas of your photo. Watch it now.
I had a very biased opinion against the Lensbaby and that was very foolish of me. It's actually a great creative tool that can have a big effect on your photos and the impact your photography can have on others.
I bought one and it's a lot of fun to play with.
And for DOF Geeks ....
.... there are even calculators that figure depth of field for you when you really need to have precise focus sharpness control.
These are also great for those photographers who may just be curious on how all of the different DOF factors come together and are related.
Have fun experimenting with your DOF!