Screenshot taken from video.
It is a popular belief that people appear to be about ten pounds heavier in photographs or videos in comparison to what the normal human vision perceives. One of the latest videos published on Scishow’s Youtube channel explores this myth by taking a closer look at the phenomena from a scientific point of view.
Based on the in depth video explanation, there are two main reasons affecting the heavier look of people captured by the camera. The two reasons are; the monoscopic vision of a single lens used in a camera and; the choice of different focal lengths of the lens used affecting varying perspective outcomes.
The most obvious reason of the difference in perception between human eyes and how the camera sees the world is the stereoscopic vision of two human eyes versus the single lens capturing the image. Using two eyes provides an important sense of depth in the images, hence our vision is three dimensional, allowing us to discern the sides of the human face and body as curves. The camera with one lens simply cannot record this information, and the entire shape of a subject is projected as a single entity, hence a flatter image measures the far sides much wider, creating the perception of larger facial or body features.
The second reason described in the video is also known as the perceptive distortion and background compression effect in general photography language. Using a wide angle lens, the image is susceptible to more perspective distortion, generating a more disproportionate human face when shooting up close (bigger face to body ratio). However, using a longer telephoto focal length eliminates this problem as the narrower perspective compresses the background of the subject. Consequently, the result of a longer telephoto focal length is a flatter image, which may also make the face appear wider than it would be being shot with a wide angle lens.
Ultimately, understanding the proper use of focal lengths and how they affect the perspectives captured in images can greatly help improve photography, especially shooting portraits of people. There is no right and wrong when it comes to which perspective or focal length to use, it all comes down to the final outcome and effect you intend to achieve in your images.