Understanding the Relationship and Effects of Focal Length, Depth of Field and Aperture

One of the great advantages of modern digital cameras is that you can instantly see the results of the pictures that you have taken and erase those that don’t meet with your expectations. If you’re still using a 35mm single reflex camera, or even a more sophisticated 6 x 6 camera, you don’t have that luxury.

So it is important to know what you are trying to achieve with each picture, and know how to adjust your settings appropriately, so that you get the results you want, hopefully with the first shot.

photo by D. Sinclair Terrasidius

There are certain situations that will not wait for you, such as fast-moving scenes, (a sporting event, or an airplane flying by). If you have time to make the proper adjustments ahead of time, you will have a better chance of capturing that once-in-a-lifetime moment. To do this, you have to understand the basic principles behind the optics involved in cameras and how they interact with each other.

Let’s Start from the Beginning

There exists a delicate balance between the aperture that you choose and the depth of field that you will get as a result. Let’s start out the quick review of what aperture is and how it works.

Different Lenses Have Different Characteristics

It is important to recognize that different types of lenses, besides giving you a different view through your viewfinder (or screen on your digital camera) also have different optical characteristics that both affect the aperture and the depth of field.

So How Do I Take the Picture I Want?

There are so many variables that sometimes people get confused about how they should set the camera up to get the picture they want. It must be also noted that most “point and shoot” digital cameras sometimes don’t even offer a lot of control over the picture itself. They often have some predetermined settings, such as “landscape” or “night picture”, or even “sports” which automatically adjust all the settings, but take control away from the photographer. More sophisticated digital single lens reflex cameras and traditional 35mm cameras offer far more control.

Follow these general guidelines: