Depth-Of-Field Preview is perhaps the most ignored featured found in camera’s. Most of the people don’t either know of its presence in the first place or if they are aware of it, they don’t know how to use it. To tell you the truth, its not difficult to learn what it does & know how to use it. Its very simple & once you know it, you’ll most often be using it. Let me show you how.
First, let’s talk about Depth-Of-Field(DOF). Depth-Of-Field is one of the most crucial factors when it comes to making a photograph. A good photograph often showcases proper use of Depth-Of-Field. Depth-Of-Field in simpler terms is the area in your photographs which is in acceptable focus(sufficiently sharp). A good photographer should be able to utilize DOF correctly so as to keep the subject as the main focus point which creates an appealing photograph.
As we set an aperture to suit a certain frame & look through the viewfinder on our camera, the camera doesn’t changes the aperture to the one we have set rightaway(Its is changed when you release the shutter). It still shows the image in the viewfinder at the maximum aperture(minimum F no.) the lens allows at a particular focal length. This is done, so you can get a bright viewfinder display & can frame easily. In such a case, if you want to preview the effect of a certain aperture the DOF preview button needs to be pressed & held as you look into the viewfinder. The button is generally found below the lens mount on either of the sides(depending on manufacturer) & often it is unmarked. Now the camera will set the aperture you’ve dialed in & give you a preview as to how it will affect the DOF. However at times, its very difficult to find out how much area is in focus & how much is not in the tiny viewfinder. In such a case(& always), I strongly recommend you use Live View. It is much easier to check the DOF in live view. The procedure remains same, switch the camera’s live-view on & then keep the DOF preview button pressed, the screen should display the DOF changes. Still finding it tough to discern the DOF changes, hit that zoom button(one you use to zoom into images) & you can magnify while you keep holding the DOF preview button. Still want to see the changes more fluidly, tether the camera to your computer & check the DOF preview on big screen else via camera’s HDMI-out attach an external monitor on field.
There you go, you’ve learned DOF Preview. Now try it & see how it can prove useful for shooting macro, portraits & almost all genres of photography.