Focal length v Compression & Expansion v MythRecently during Zack Arias' creativeLIVE course I discovered (among a gabillion other things) that focal length choices can have a considerable impact on the background behind the subjects in our photographs. Notably, that wide angles can expand the background by pushing objects in the background away while telephoto lenses can compress the background by pulling objects in the background closer. Within hours of hearing Zack's argument, I heard a counter argument that suggests that focal length has no effect on the background behind the subjects in our photographs.
What I've come to notice over the various arguments on either side of this debate is something so simple, yet so complex. All of these arguments come back to the basic principle of The Order of Operations. For those that haven't taken a math course recently (myself included) allow me to elaborate:
When are present with a problem like the following example, there are certain methods we are taught that help us solve the problem.
8 + 5 x 3 – 7 ÷ 2 = ?
If we simply move from left to right we get an answer of 16, and 16 is a real number that exists in real life. However, if we follow the rules our old, decrepit math teachers gave us (PEMDAS*, being Parentheses-Exponents-Multiply-Divide-Add-Subtract) we get an answer of 19.5 which is also a real number that exists in real life. So why the different result? When we approach a problem where we start has a direct and considerable result on the final solution.
How does this apply to photography? Easily: If you change the order of events in which you take a photograph it can have a considerable difference in the end result. We have several factors to consider when making a photograph:
- Camera-to-subject distance (working distance)
- Camera-to-background distance
- Focal length
- Framing/Composition
- Bokeh/DOF/ad nauseum
For instance, in my friend John Cornicello's example he started thinking about a photograph with the working distance or camera-to-subject distance. This factor was the first thing he thought of before lifting the camera to his eye. John is a portrait photographer, so we'll have him start with a simple headshot. I believe he started with a distance of 5 feet. From there he decided on a lens that would fill the frame as he desired (headshot, eyes only, 3/4, etc). In this example, he didn't state whether or not the background was a consideration for the photo. Since the background isn't mentioned, it's possible that it's unimportant to the photograph, but let's assume we don't want distracting elements growing out of our subject's head (head in a clean spot). For his example the focal length he chooses
would not effect the compression or expansion of the photograph because the camera-to-subject difference
does not change. His working distance is the “boss” of this photograph, followed by composition, and then focal length. This order of operations produces a real result that we can see in real life.
The opposite side of the argument changes the order of operations. When I start thinking about a photograph I have a Frame/Composition in mind before I even think about lifting a camera to my eye. I'm a portrait photographer, so I start with a simple headshot: let's say, a bust shot... from just below the crown of the head to mid-chest level. This person is the subject of the photograph, so I've decided the background is unimportant to the photograph (to closely match the previous example). At this point, the frame is decided and we can decide on a focal length. We look at the background and decide what focal length will give us the subject's head in a clean spot. If we choose a wide angle lens, the camera-to-subject distance would be closer than if we choose a telephoto lens. Because we've already decided on a frame and composition, the camera-to-subject distance
must change based on what lens we decide on in order to satisfy this requirement. The wide angle lens
will push the background away because our camera-to-subject distance requires us to be close in order to satisfy the pre-visualized composition. The telephoto lens
will pull the background in because our camera-to-subject distance requires us to be further away in order to satisfy the pre-visualized composition. If the wide angle lens will not allow us to have a headshot with head in a clean spot (our pre-visualized composition), another lens choice
must be made; possibly a telephoto lens. The opposite is also true: If the telephoto will not allow us to have a headshot with head in a clean spot another lens choice
must be made, possibly a wide lens. (For the exhibit below, any focal length over 80mm would work just fine.) My composition is the “boss” of this photograph, followed by focal length, and then working distance. This order of operations also produces a result that we can see in real life.
In John's example, no compression or expansion is evident regardless of what focal length he choses because the camera-to-subject distance
does not change. The first thing he decided on was working distance. This order of operations is valid and produces the results that John has posted elsewhere.
In my example, compression or expansion is clearly evident based on the chosen focal length because the camera-to-subject distance
must change based on the composition. The first thing I decided on was my frame and composition. This order of operations is also valid and produces the results that I have posted here.
Because both examples are repeatable and reproducible, it verifies claims on both sides of the fence. The fact that focal length has an influence over expansion and compression is evident in the photos, but can only be witnessed when an experiment is performed in a way that shows it; saying that the phenomenon doesn't exist is ludicrous. Not performing the experiment with the correct values will have an effect on the outcome. This is akin to trying to produce the color "green" when you only have "red" and "blue" to work with; Only "purple" is possible, but we all know that "green" is a color that exists. However, if the experiment calls for "blue" and "yellow" of course you can produce "green", but "purple" cannot be made from this combination.
The above is precisely reason why the focal length / expansion / compression issue exists. Depending on the order of events that we approach making a photograph it can completely change the result that we see in real life. Neither approach is wrong or right; It's simply indicative of the order of operations. In these examples we didn't even include depth of field or other factors that we can include into our photographs. More factors means more potential changes in the order of operations.
Of course, you may feel free to argue all you want, but both experiments are performed here. Please do me a favor and make your arguments intelligible though. :-)
*Please note that some old guys fought over which order of operations to follow before they made us adhere to it. They decided on PEMDAS and sent the other-side-of-the-fence-guys to Mycenae or something.
**Also note that my 6-year-old does her best to stand still for these boring photos, but the bribery of ice cream usually does the trick. She just looks so sad...
