Understanding the Core Principle: Perspective Compression
The key concept is perspective compression. This isn't about *actual* compression of the face, but rather how the relative distances between elements within the frame (e.g., nose to ears) are rendered.
* Short Focal Lengths (e.g., 24mm, 35mm): Exaggerate Perspective, De-compress Distances
* Wider Field of View: Captures more of the background, which can be distracting or useful depending on the desired look.
* Nose Appears Larger: The nose, being closer to the camera, appears disproportionately large compared to the rest of the face. This is because the distance between the nose and the ears becomes more pronounced in the image.
* Ears Appear Smaller and Recede: Ears and the sides of the face seem to be further away, making the face appear wider and potentially more distorted.
* Distortion: Can introduce noticeable distortion, especially at the edges of the frame. This is more pronounced in very wide-angle lenses (e.g., 16mm or wider).
* Look & Feel: Often used for environmental portraits, showing the subject within their context. Can be unflattering for close-up portraits due to the exaggerated features. Can be used creatively to create a sense of drama or a quirky look.
* Normal Focal Lengths (e.g., 50mm): Relatively Accurate Perspective
* Close to Human Vision: Offers a perspective that is somewhat similar to how we perceive faces in real life.
* Balanced Proportions: Provides a generally flattering representation of facial features, with a more natural relationship between the nose, eyes, and ears.
* Versatile: A good starting point for portraiture.
* Look & Feel: Creates a realistic and approachable portrait.
* Long Focal Lengths (e.g., 85mm, 100mm, 135mm, 200mm+): Compress Perspective, Compress Distances
* Narrower Field of View: Isolates the subject, blurring the background.
* Nose Appears Smaller: The nose, though still closer, appears relatively smaller compared to the rest of the face. The distance between the nose and ears is compressed.
* Flatter Facial Plane: The face appears more two-dimensional, with less emphasis on the depth between features.
* Ears Appear Closer to the Face: Sides of the face and ears don't recede as much, making the face appear narrower and more compact.
* More Flattering: Generally considered more flattering for portraits because they minimize distortions and create a more idealized representation.
* Look & Feel: Creates a polished, professional, and often romantic portrait. Background blur (bokeh) helps isolate the subject. Requires more distance between the photographer and the subject.
Specific Examples and Considerations:
* 24mm-35mm: Avoid using very close for standard portraits unless you're deliberately going for a dramatic or distorted effect. Best suited for environmental portraits.
* 50mm: A classic and versatile focal length. Good for headshots and upper-body portraits. Requires getting closer to the subject.
* 85mm: A very popular portrait lens. Offers excellent background blur and flattering perspective. Requires more distance from the subject.
* 100mm-135mm: Excellent for tighter headshots and portraits where you want to emphasize the subject's eyes. Allows for more distance, which can help the subject feel more relaxed.
* 200mm+: Can create incredibly shallow depth of field and compressed perspectives, but requires a lot of space and can feel isolating for both the photographer and subject. Often used for action shots and portraits from a distance.
Beyond Focal Length: Other Factors Matter
It's important to remember that focal length is just one factor. Other elements contribute to the final look of a portrait:
* Camera Position (Distance to Subject): Changing your distance to the subject will also impact perspective. If you use a wide-angle lens but stand far back, you won't get the same exaggerated effect as if you were close.
* Aperture: Controls depth of field (background blur).
* Lighting: Significantly affects the shape and texture of the face.
* Posing: The way the subject holds themselves drastically influences the overall look.
* Subject's Facial Structure: Some faces naturally lend themselves better to certain focal lengths.
Experimentation is Key
The best way to understand the impact of focal length is to experiment. Take the same portrait using different focal lengths and compare the results. Pay attention to how the shape of the face changes, how the background is rendered, and how the overall mood of the image is affected. This will help you develop an eye for choosing the right focal length for different subjects and situations.
In summary, focal length dramatically changes the perceived shape of a face in portraits by altering perspective. Short focal lengths exaggerate features (especially the nose), while long focal lengths compress and flatten them. Understanding these effects is crucial for creating flattering and expressive portraits.