Do you ever take pictures for one reason and then later find a use for them beyond their original purpose? That is what happened to me on a recent hike. At the top of the mountain where our group stopped for lunch I took pictures of us with the mountains in the background. After reviewing the pictures I found that I used a variety of focal lengths and thought it would make a great tutorial on the effects of focal length.
Now for those of you who love physics and want the technical explanation you can go to wikipedia. The rest of this post will focus on the effect of focal length with as little technical jargon and how to use it to compose your photos.
But first, lets get the technical part of the discussion out of the way in one paragraph. Focal length is measured in millimeters. The shorter the focal length is the larger the field of view will be and the more of the scene you are photographing will fit in the picture. The longer the focal length is the smaller the field of view will be and less of the scene around you will fit in the picture but what is in the picture will be magnified to be closer. The easy way to remember this is the longer focal length (the larger the number) the more you are “zoomed in”. The shorter the focal length, the smaller the number, the more you are “zoomed out”. Zooming out shows you more information and allows you to fit more in your frame. Zooming in allows you to focus on a particularly feature.
Still with me? Good. Focal length has one other effect on composition. It changes how close object appear to be to each other. The longer the focal length the closer objects appear together, the shorter the focal length the farther object appear from each other.
So I lied and that was two paragraphs but let us look at what this does in our photos.
To demonstrate the effects of focal length I have three picture taken at 3 different focal lengths. First lets take a look at a photo taken with a focal length of 45mm.
Here we can see myself at the top of Elk Mountain looking at the cascade mountains in the background. Over my right shoulder is a mountain known as the Canada Border Peaks as it is just on the Canadian side of the US/Canada Border. The 45mm focal length is considered close to “normal” meaning objects look about the same distance in photos as they do in real life. Now lets take a look at how a wide focal length of 16mm changes how the scenery looks.
The wider focal length (e.g. Zoomed Out) has captured a wider field of view. Not only can we see the Canada Border Peaks in the photo, but we can see many other mountains as well. Also take not of how far away the Canada Border Peaks look now. They appear small and a great distance away. The final example I zoomed in using a focal length of 80mm.
Here the hikers are sitting right where I was standing in the last two photos. The Canada Border Peaks looks much closer than in either of the two photos, even thought the subjects have not moved positions. The field of view is also narrower. I purposely chose this longer focal length as it allowed me to show off our hiking group while emphasizing the scenery.
So how do we use focal length to our advantage when composing our photos? If we want to separate our subjects from the background then we use a shorter focal length (zoomed out). If we want to compress our subject and the background as I did with the last photo, then we zoom in and use a longer focal length. If we need to include a wider field of view to capture a larger scene we can use the shorter focal length and if we want to focus on a feature farther away we need a longer focal length.
With digital cameras it is easy to experiment. The best way to learn is to try this out. Simply set up some objects and photograph them using different focal lengths.