Focal Length for Portrait Photography - Zoom for Refined Pictures of People
What is the best focal length for portrait photography? In other words, if you are using a zoom lens, what is the best zoom position for taking a picture of one or more persons? What's different between a close-up and a full-length portrait? Answers to these questions will let us make more refined images of the people we love to photograph.
In order to answer these questions we first must focus on what we want to do. Usually we want two things:
1) Reproduce the persons with no distortion.
2) Throw the background out of focus to avoid a distracting backdrop.
To fulfill point 1) we should avoid getting too close to our subject. So this in turn leads to the question: what is the correct distance from the subject? The answer is twofold, according to whether you want a close-up or rather a 3/4-length to full-length group portrait.
If you are making a close-up, a short telephoto is the best choice, let's say an 80mm lens. Such a lens offers normal perspective, while a standard 50mm lens would force the photographer to get too close to the subject thus altering the perspective (a phenomenon known as "foreshortening"). If foreshortening occurs, the closer parts of the subject's face (the nose, the chin) would appear greater than they are, and the opposite would happen to the back of his or her head. Or, in case of a large group, the faces of the people in front would appear much greater than those on the back. That's why, in case of a large group, an even longer lens than the 80mm would be better. If a 200mm is used for a close-up group portrait, the background will be completely out of focus, if this is what you desire, thus fulfilling the previous point 2). This is because the longer the focal length, the shallower the depth of field (even though this is rather improper). Be careful, however, to put all the faces in the same shallow plane of focus. Finally, avoid using extreme telephotos (300mm) because, again, perspective becomes distorted, with all subject's features appearing compressed. Moreover, keep in mind that the closer to the frame edges, the stronger the distortion. This is even more so for wide-angle lenses.
If you are making a 3/4-length or full-length group portrait, a standard 50mm lens is the optimum choice. This time you will be farther away from the subject and the aforementioned foreshortening will not take place. Unfortunately, with such a lens it will be impossible to separate the subject from the background, thus rendering difficult the fulfillment of requirement 2). The best you can do is using it with wide aperture, because this too helps reducing the depth of field. This recommendation holds true even when the photographer is forced to use a wide-angle lens to fit a big group into the frame and still maintaining a reasonable working distance.
Just in case you are using a compact digital or film camera with a zoom lens, if it has a 3x zoom, its focal length will be something like 35mm when completely zoomed out (wide-angle position) and 105mm when completely zoomed in (telephoto position). On the other hand, if you possess a 10x zoom lens it will be about 35-350mm. These equivalences will help you apply the recommendations of this article.
Andrea Ghilardelli runs an online photo retouching service. For more articles and to get your photographs transformed into something special, please visit his site: www.ilghila.com.