Understanding the Key Concepts:
* Perspective Distortion: This refers to how the relationships between objects in a scene are rendered. Wide-angle lenses exaggerate perspective, while telephoto lenses compress it. This is the *primary* reason for facial distortion.
* Compression (or Telephoto Compression): Telephoto lenses make objects in the background appear closer to objects in the foreground. This "compresses" the apparent depth of the scene.
* Working Distance: The distance you, the photographer, stands from your subject. Changing focal length often necessitates changing your working distance to maintain the same framing of the face. This distance *also* contributes to the perceived distortion.
The Effects of Different Focal Lengths:
1. Wide-Angle Lenses (e.g., 24mm, 35mm):
* Exaggerated Perspective: The nose appears larger and more prominent because it's closer to the camera. Features further back (like the ears) appear smaller and further away.
* Distorted Facial Proportions: The face can look stretched or widened, particularly at the edges. The jawline can seem less defined.
* Flattened Features: While technically perspective is exaggerated, in some cases, the face may appear somewhat flattened as features are pulled toward the camera.
* Intimacy: Wide angles require you to be very close to your subject, creating a sense of immediacy and intimacy, but potentially at the cost of accuracy in representation.
* Best Used for: Environmental portraits, where you want to show the subject within their surroundings, or for more artistic/stylized portraits with intentional distortion.
2. Normal Lenses (e.g., 50mm):
* Relatively Accurate Proportions: Often considered a good starting point because they render the face in a way that's generally perceived as more natural and balanced.
* Good Working Distance: Allows you to be a comfortable distance from your subject without being too far away.
* Versatile: Can be used for headshots, waist-up, or even full-body portraits.
* Not Dramatic: May not be as visually striking as using wide-angle or telephoto lenses for a specific artistic effect.
3. Telephoto Lenses (e.g., 85mm, 105mm, 135mm, 200mm):
* Compressed Perspective: The face appears more compressed. Features look closer together, and the distance between the nose and ears seems reduced.
* Flattering Proportions: The flattening of the face tends to be considered more flattering by many because it reduces the prominence of the nose and softens other features.
* Rounded Face: The face tends to look rounder and fuller, particularly at longer focal lengths.
* Shallow Depth of Field: Telephoto lenses make it easier to achieve a shallow depth of field, blurring the background and isolating the subject.
* More Distance Required: You need to stand further back from your subject to achieve the same framing as with shorter focal lengths. This can make it harder to communicate or direct your subject effectively.
* Best Used For: Classic portraiture, headshots, and situations where you want to minimize distractions in the background and achieve a flattering rendering of the face.
In Summary (The Key Takeaway):
The effect of focal length on facial shape is primarily due to perspective distortion. Wide-angle lenses exaggerate the relative size of closer features, while telephoto lenses compress the distances between features. You can also influence the shape of face by changing the distance from the subject.
Tips for Choosing a Focal Length:
* Consider Your Goal: What kind of portrait do you want to create? Naturalistic? Artistic? Flattering?
* Experiment: Try different focal lengths to see how they affect your subject's face.
* Think About the Background: How important is the background to the portrait? A wide-angle lens can include more of the environment, while a telephoto lens isolates the subject.
* Communicate with Your Subject: Let them know why you're using a particular focal length and how it might affect their appearance.
* Don't Be Afraid to Break the Rules: These are general guidelines, but the best focal length is the one that helps you achieve your artistic vision.
Example:
Imagine you're taking a portrait of someone with a slightly larger-than-average nose.
* Wide-Angle Lens: The nose will likely appear even larger and more prominent, potentially drawing unwanted attention to it.
* 50mm Lens: The nose will appear closer to its actual size, a more natural rendering.
* 85mm or Longer Lens: The nose will be slightly compressed and appear less prominent, which many people find more flattering.
By understanding how focal length affects perspective, you can make informed decisions to create portraits that are both aesthetically pleasing and accurate representations of your subjects.