Zoom lenses are the most common lenses by far. You can’t even buy a camera kit without one. Many photographers today do not have the experience of working with a single focal length lens - I suspect that many folks don’t even know they exist. I remember years ago traditional photographers using the old line, “Yeah, I have a way of making my lens show more or less of the subject. It’s called using my feet!”
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DSLR Camera Lenses: How to Use Your Feet
There is something about “using your feet” that is not simply a joke. Focal length is more than simply a way to change your composition by zooming in on the subject or zooming out to show more of the environment. As you change your position, you change perspective, then the focal length allows you to see those effects. This is such an important part of lens usage that it used to be a critical part of any photographer’s learning years ago. But now with zoom lenses, this understanding of the relationship of distance, perspective and focal length is often ignored, which means really limiting your tools.
First, as you move close to a subject and zoom out (wider angle), you are strongly influencing perspective. Simply zooming from a fixed position does not affect perspective. Perspective can be an important factor in photographing a subject. Perspective is how distance appears in your photograph and is affected by space and relationships of objects from near to far. Perspective can be deep, shallow or anything in between.
As you get close with a wide-angle, perspective gets deeper. The subject gets larger in relation to the background, and the background gets smaller.
As you back up with a telephoto, perspective gets shallower. The subject gets smaller in relation to the background, the background gets larger. Stuff looks much closer together.
Right there, you have two important uses of focal length that go beyond simply zooming in or out for composition. With the wide-angle, you can make the subject look very dominant and the background small. That can also make the background highly recognizable no matter what you do with the subject. With a telephoto, you can significantly change the background by enlarging it. This allows you to take a relatively small part of the background (a shadow, for example) and make it large behind the subject. Since the background gets larger, sometimes you only see a small part of that background, a hint, so to speak, rather than everything.
These effects can be very strong. A great way to really understand this is to do an exercise with your zoom. Go out for a photo shoot in some interesting area. Alternate every shot from the widest part of your zoom to the most telephoto.
In other words, take the first photo with the widest-angle setting, then zoom into the most telephoto and look for a new subject. Alternate back and forth between the extremes (no cheating by using middle focal lengths!) as you take at least 20-30 photos (more is better). That will teach you more about focal length than almost anything else because it forces you to see focal length and not use zooming to fix compositions. Watch what happens to backgrounds, to space, to the appearance of distance, to depth of field.
To ramp up your learning, add in this twist. Shoot the same subject for each pair of shots from focal length change and (and this is very important) move physically closer to the subject with the wide-angle and back up with the telephoto to keep the subject roughly the same size. Then you really have to look at what is happening to the whole photo. Working with focal length in this way is one of the most challenging parts of my Impact in Your Photographs: The Wow Factor online course at BetterPhoto.com because most people are used to just zooming. I also cover this topic in a number of my books, including The Magic of Digital Landscape Photography.
Another effect you will notice is a strong change in the appearance of depth of field (the technical purists can prove that arbitrary depth of field does not change, but since you are changing focal length, you change what is seen in the photo which changes the apparent depth of field — that’s what we care about anyway). Wide-angle lenses give more depth of field than telephoto lenses (or focal lengths on a zoom). That is true even for a wide-angle or telephoto only zoom — then the wider focal length gives more depth of field than the narrower angle focal length.
So ultimately, focal length has a strong effect on perspective (and appearance of space) and on depth of field. These are two important uses of focal length that cannot be accessed simply by zooming. So you can indeed do a lot more with a zoom than simply zoom in and out on the subject!
More on Rob Sheppard...
Rob is the editor at large for Outdoor Photographer and Digital Photo magazines. See his instructor bio and a listing of his courses here...
Also check out BetterPhoto's school of photography and its other online digital photography courses. BetterPhoto also offers special certification for photography.
About Author / Instructor / Photographer, Rob Sheppard
Rob Sheppard has had a long-time and nationally recognized commitment to helping photographers become better photographers, regardless of the equipment and technology. He was the editor of Outdoor Photographer magazine for 12 years and was the original editor of PCPhoto (now Digital Photo). Now he is editor-at-large.
He is also the author/photographer of over thirty photo books, including The Magic of Digital Landscape Photography, The National Geographic Field Guide to Photography - Digital, and Adobe® Photoshop Lightroom for Digital Photographers Only. He writes regularly for Outdoor Photographer and teaches around the country, including workshops for the Palm Beach Photographic Centre and the Light Photographic Workshops. His Web site for workshops, books and photo tips is at www.robshepppardphoto.com, and his blog on nature and photography is at www.natureandphotography.com.
As a photographer, Rob worked for many years in Minnesota (before moving to Los Angeles), including doing work for the Minnesota Department of Transportation, Norwest Banks (now Wells Fargo), Pillsbury, 3M, General Mills, Lutheran Brotherhood, Ciba-Geigy, Anderson Windows, and others. His photography has been published in many magazines, ranging from National Geographic to The Farmer to, of course, Outdoor Photographer and PCPhoto.
He and his wife, Vicky (married 30+ years), live in the Los Angeles area. They have a son working on his Ph.D. in youth sports and education, and a daughter studying communications/journalism.
Also see Rob's Nature and Photography blog.