What is Depth of Field? How to use it to control sharpness

Many photographers have no clue about what the Depth of Field (DOF) preview button on their camera does. A good number have actually attempted to press the button, which got them disappointed when everything went dark while viewed though their viewfinders. And so to speak, have never attempted to press that button again. But wait…

The moment you learn about what the DOF preview button does, it will definitely be hard for anyone to convince you to take a single shot without using it. So what exactly is Depth of field preview button? And what exactly does it do?

Well, the DOF preview button allows you to preview the depth of field of the image you’re about to shoot—prior the actual shooting, the same way it would appear in the final image. In other words, the preview will help you establish which section of your photo will be sharp and which one, blurred.

Here’s how it works: for landscape photos with sharp images that are in focus, the depth of field will expectedly be deeper, as opposed to portraits whose subjects are in focus but the background is blurred.

In brief, the DOF preview button enables you to see how the actual image will actually look like after you’ve taken the final shot. It starts by stopping the aperture you’ve set the moment you press the button. This enables the final image to appear in your camera’s view finder for you to see before deciding on whether or not you’re going to take the shot.

Why is it important?

Many beginners waste too much time taking so many photos while playing around with aperture settings between the shots to see which setting has the best shot. But with DOF preview button, you can easily preview the background blur and sharpness—depending on what you want, and make all the necessary adjustments before taking one sure shot.

The typical viewfinder in your dSLR only shows you how the scene will look like when the lens is set at the widest aperture. This works well if you’re planning to see how the scene will look like under excessive brightness, but when it comes to determining where your focus and depth of field is located, only the DOF preview button can help you with that.

Now the best way to use the button is to try and shift your focus on the background of the image you’re planning to shoot. This will save you the trouble of getting distracted along the way, particularly for rookies.

But for advanced snappers, the button will help you work out the exact location to place your focus for total sharpness on the subject and minimal depth of field on the background to blur it.

How to use it

The button may be placed in different regions. But in most cases, it’s situated close to the lens, to make it easy for you to use your thumb or forefinger to press it without strain.

For a starter, it’s easier to test the button by setting your camera to aperture priority mode. You can begin with the widest maximum aperture (such as f/3.5), after which you can press and hold the DOF preview button down. Next, try to close the aperture down making small increment in the f-stop (from f/5.6, f/8, and lastly f/11) and pressing the button to see the effect each adjustment brings.

Every time you close the aperture, the scene becomes darker when viewed through the viewfinder. The camera also slows down the shutter speed when you take photos, to compensate for the narrow aperture, as it attempts to maintain exposure.

When not to use it

The DOF preview button works best in bright light situations. Otherwise you’re likely to have a hard time seeing anything clearly when you look through your viewfinder.

In case you find yourself using your camera under low light conditions, try pressing the button with the camera in live view mode. Depending on the other settings, the image on your view finder should be bright enough to be clearly seen.

More work for the DOF Preview Button

Some snappers may not find the DOF preview button very useful. Taken together, you can still review the images you’ve taken on the screen to check the depth of field and focus from there. But when you’re only limited to one shot, you’ll definitely need the DOF to take the shot.

Advanced photographers understand what we mean by reversing the lensing or freelensing techniques. You see, for lenses that don’t come with a physical ring aperture in their barrels, the DOF button allows you to stop down the lenses, so you can separate it from the dSLR body that’s set to a specific aperture. That’s exactly where photography techniques such as freelensing and others come in.