In figure B above, a 21mm wide angle lens expands its reach at 74 degrees.  Looking at the lines you can see a rough example of the field of view.  As you zoom to 200mm, the field is reduced to a mere 12 degrees.  That changes what the camera will capture tremendously.  For comparison, humans see (clearly with detail, not peripheral vision) at about 50mm, also represented in the diagram.  This is the chosen focal length for many portraits because the proportions of the subject are similar to how our eyes see them.  Do what?????  I thought zooming in and out just changed the size of the subject.

Yes, you are changing the size of the subject but you are also changing the relationship between elements as well.  Looking at the diagram on the right of figure B you can (hopefully) see this.  The wider the angle, the more difference there is between foreground and background.  As you zoom, the lens captures elements in a more linear fashion to where the relationship stays closer between up close elements and those in the background.  This is because with the wider angle, the camera will capture much more of the scenery and what is closer to the camera will become more predominant due to its proximity to the lens.  As you zoom in, you are normally excluding what is close to the camera and only including that which is further away.

What does this mean to me, I'm confused?  That's OK, its a weird concept to explain, and harder to understand.  This is what it means.  You can emphasize a bit of foreground by using a wide angle lens and getting close to the object.  It will appear much larger than it actually is because the lens is very close to the subject.  Keep in mind that the background will be expanded causing it to appear smaller and more distant.  If the background is more important and you want to change the relationship you would need to back up to another shooting location and zoom in to a longer focal length.  You can still include the same foreground and background, but the background all of a sudden appears larger and more prominent in relation to the foreground which has been reduced in apparent size.  This is because the subjects' distances from the camera is more closely related.

Whoever said a photograph doesn't lie was pulling a fast one on us.  A photograph is the ultimate liar.  By choosing a focal length, you can make a leaf appear larger than a house, or a shell appear larger than a boat on the ocean.  You can also compress the foreground and background so that the apparent distance between the two is shortened.  This is a very powerful tool and one that can really set a picture apart from others of the same subjects.


How does this really work?

Lets look at some examples of the creative use of focal lengths to really get an idea of what can be accomplished with this creative tool.  Lets look at wide angle photography first.  There are times when you need the wider focal lengths to capture large subjects which are up close.  In the following example captured at Hanging Rock State Park, I would have been unable to include as much as I have without backing up if I were using a "normal" lens.  The problem was there was nowhere to back up to without falling off of the rock outcropping I was standing on.


Jagged Precipice  Captured at around 17mm

There are other times when a wide focal length is needed in order to emphasize the foreground for some added visual pop.  The following photograph illustrates this quite well.  I wanted to capture both the observation tower as well as a clump of wildflowers.  The problem was, the tower was dominating the wildflowers, and they would get lost in composition with a "normal" lens.  By selecting my ultrawide lens, I was able to dramatically capture the small clump of wildflowers (only about an 8x6ft patch) against the tower.  An added benefit was being able to capture the clouds above.


The Observation Tower   captured at around 16mm

Here is another example where a fountain was used as the primary focal point for the image, but I wanted to include a nice section of the downtown skyline.  By getting very close to the fountain, and using a wide focal length, I was able to capture all that I wanted, and with the exaggerated perspective on the fountain.  It was this exaggerated perspective that really showcased the primary element in my composition.


Urban Oasis   Captured at about 20mm

Now you see some of the interesting effects that can be introduced with the wide angle end of the spectrum.  The "normal" focal length which is around 50mm is not as impressive compositionally as the others because it is what we see with our own eyes.  Relationships between elements, as well as their apparent distances are kept in tune with what we are used to.  This is not a bad thing at all, and can actually be very helpful in our compositions.  There are times when you see something and everything just fits together like it appears to your eyes.  This is when you know you need that "normal" focal length to capture your image such as this image from Historic Bethabara.


Log Cabin   captured at around 45mm

Telephoto focal lengths are when it gets real interesting.  The first time you look through a long telephoto lens, you will be amazed.  It really looks like you can reach out and touch the scene through your camera.  This is probably the most used feature of the telephoto range of focal lengths.  There is just no substitute when your subject is off in the distance, and you want to fill the frame.  This is where wildlife shooters really benefit such as this image of a very small bird.  There is no way I could have gotten close enough to snap this with a "normal" lens, but with a long telephoto it was no sweat, and there was very little chance of me frightening him.


The Red Eye   captured at about 600mm

Wildlife isn't the only subject that benefits from being able to reach out and grab some distant details.  There are times when you just can't get close enough to your subject with a "normal" lens.  Such was the case with this bit of fall foliage.  It happened to be across a fairly steep and rugged ravine.  It would have been rough to cross over, but from the opposite bank, I was about 75 yards away from it.  Using a long telephoto lens I was able to isolate a small portion which included just what I wanted without any extraneous detail.


Thinning Foliage   captured at about 500mm

So, what about this compression thing that I've been talking about with telephotos?  Well, you can see a bit of it in the photograph above.  Distances are skewed, but not too bad because the elements were very close to start with.  I have another example which shows how this works a little bit better.  In the following example, the tree in the foreground is about 100 yards from the barn in the distance.  Using a wide angle lens right at the tree would all but make the barn disappear.  A normal lens would capture the tree, but the barn would get lost in the background.  However, by moving back well away from the tree, I was able to change the perspective of the two primary elements.  The tree was smaller now because I was about 75 yards away from it now.  All of a sudden, the barn wasn't that much further away.  Using a moderate telephoto, I was able to compress the distances (visually) and make the barn larger than it appeared to my own eyes.


Change in Tempo   captured at about 125mm

As you can see, there is a lot more to focal length than just zooming in to fill the frame.  Perspective is not without its trade offs though.  When you are selecting your focal length, or your lens, you need to keep a few things in mind.  As with everything else in photography there are compromises that have to be made, some are good and some are not so good.


Focal Length Compromises

Just when you thought you were starting to grasp focal length, we are going to throw a curve ball at you.  Focal length also affects your depth of field.  As a general rule, the longer the focal length, the narrower depth of field that you will have.  What that means is at a constant f/8 aperture, you will have a much wider field of sharp focus with a short focal length than a long one.  This is great for ultra wide angle photography.  This focal length is usually reserved for the landscape photographer who desires sweeping landscapes to be in total focus and tack sharp.  With a wide angle lens stopped down to f/22 or narrower, the photographer can focus on a foreground element inches in front of their camera and still get a distant background in apparent sharp focus.


In Constant Turmoil    Captured at about 17mm at f/22

While wide angle shots benefit from increased depth of field, telephoto shots see the opposite.  Depth of field decreases at focal length increases.  What that means is you will need a very narrow aperture in order to keep relatively close objects in apparent focus.  However, many times when you get into the longer focal lengths, you are working on wildlife which much like portraits can benefit from a narrow depth of field.  All of a sudden, that slow f/5.6 lens is acting like an f/2.8 "normal" lens when it comes to depth of field.  Unfortunately though, the actual speed of the lens is not affected in the same manner.


Overseeing   Captured at about 320mm at f/4.0


Rosy Outlook   Captured at about 620mm at f/32

For the landscape photographer depth of field becomes an issue at the longer focal lengths.  As you can see above, the aperture had to be a whopping f/32 in order to keep this scene in focus and relatively sharp.  Even at such a narrow aperture, you can see obvious softening in the extreme background, but not enough to detract from the photograph fortunately.


Conclusions

As you can see, there is a lot to focal length, and how it can affect our photography.  For those wanting to venture into the artistic side of creating pictures, the use of focal length is as important as your choice of exposure.  Thought must be give to each composition in order to pick the best focal length possible.  Keep in mind its not just a matter of where you are in relation to the subject (filling the frame), but your subject's relation to supporting elements within the frame (compositional control).  You have to ask yourself how you want things to interact in your photograph, and then pick a focal length.  You will have to adjust your shooting position in order to effectively utilize your desired focal length.  There will also be times where your only shooting position dictates your choice of focal lengths.

Whether you are using a point and shoot camera or a sophisticated SLR camera what you have read here will be of equal importance.  The difference is the extent to which you can use the information here.  With an SLR you can add lenses to your kit covering all sorts of focal lengths while point and shoot users are restricted to what the fixed lens is capable of.  Rarely do these cameras go wider than 28mm which will limit your wide angle creativity.  Regardless, all cameras have some perspective control through focal lengths and you owe it to yourself to explore the possibilities.

Written by Greg A. Kiser