In this article we shall look at two terms – perspective and focal length and find out how they are related to each other (if at all). We shall also look at the effect that changing the focal length has on certain photographic situations. We shall also look at how you can make creative use of perspectives and focal lengths.
Does focal length impact perspective?
You may have heard about this statement quite often, the focal length that you use goes a long way in capturing the right perspective for your images. The statement is both right and wrong at the same time. While focal length does not change perspective per se, it does change how the subject is represented.
Why the eye-level perspective is not always best?
What you see, i.e., your perspective, is not necessarily the best when it comes to capturing a scene. By placing the camera at a particular angle, however, you may change that perspective and capture a completely fresh one, something that may have never been done before. Professional photogs often do that in order to create a unique image.
You can remove the camera from the eye level and place it on the ground to capture a bug-level perspective of a scene. Alternatively, you can shoot straight up, laying down on your back to capture an overhead foliage in a different perspective.
The right focal length for an image
You may have heard this statement – certain scenes warrant certain focal length. What is meant by that is the right focal length is important to capture a certain scene in a proper way (not necessarily a unique way). For such scenes using the wrong focal length can be disastrous. E.g., if you are shooting portrait images, using anything wider than 70mm can be catastrophic.
Wide angle lenses give you a bigger field of coverage. To fill the frame for a portfolio shot you will need to step in close to the model. Additionally, wide angle lenses tend to accentuate the size of an object that is close to the lens. What happens as a combination of these factors is that the nose of the subject (which is closer to the lens) appears larger, while the rest of the face appears slender; a rendition which no client will like! Alternatively, you cannot hope to shoot a sweeping panorama using a 300mm tele-lens. You will need an ultra-wide angle lens for that.
General purpose kit lenses such as the 18-55mm or the ubiquitous 50mm standard prime are great for everyday photography. But when it comes to shooting anything from the waist up, whilst filling the frame, the best focal lengths are usually the ones between 100mm to 135mm.
Perspective and focal length
Thus, the explanations point at two different things. Perspective is something that depends on the camera angle and how you choose to positon it in respect to the subject. Focal length on the other hand affect how the image is represented. The two are not to be confused together, despite the fact that they are sometimes used in tandem. Let’s look at a few examples.
Background compression is a type of perspective distortion that happens more with tele lenses than with wide angle lenses. Let’s take an example. Let’s say you take an image of a scene at 16mm. Now, you take another image of the same scene at 50mm. For the next two images you use focal lengths 100mm and 200mm respectively. Now, analyze the four images side by side.
You will notice that for each progressively longer focal length more of the background appears to be sucked into the image while the foreground appears pushed back. In other words the background and the foreground appears to be compressed together. This effect is ideal when you want to incorporate more of the background in your images while getting a close up of the main subject.
Forced perspective is a self-explanatory term, but yet I will attempt at explaining it for the beginners here. To understand forced perspective, first you need to understand a simple aspect of optical illusion. If you place two subjects of equal dimensions a fair distance apart and then shoot from front the one at front will appear larger than the one at back. Taking this concept forward it is thus possible to shoot a small scale model of a car by keeping an individual far behind the car and make them both look relative in size. Movie production houses have done this kind of trickery for years. Steven Spielberg famously used this in the movie ‘Close Encounters of the Third Kind’.