Understanding Perspective Compression & Elongation
The key thing to remember is that focal length itself doesn't change the *actual* shape of the face. What it changes is the perspective of the scene, which in turn affects how the face *appears* to be shaped. This is driven by the changing relationship between the size of objects closer to the camera vs. objects further away.
* Perspective Compression: Longer focal lengths (telephoto lenses) compress the perspective. This means that the difference in apparent size between objects closer to the camera and objects further away is reduced. In portraiture, this makes features like the nose and ears appear closer in size, resulting in a flatter, more compressed look.
* Perspective Elongation: Shorter focal lengths (wide-angle lenses) exaggerate perspective. Objects closer to the camera appear much larger, and objects further away appear much smaller. In portraiture, this can make features like the nose appear larger and more prominent, while the ears appear smaller and further back, creating a more elongated or distorted look.
How Different Focal Lengths Affect Face Shape
Here's a look at how various focal lengths typically affect the perceived shape of a face in portraiture:
* Wide-Angle Lenses (e.g., 16mm-35mm):
* Distortion: Can create significant distortion, especially at the wider end (e.g., 16mm). Features closest to the camera are enlarged, and lines tend to curve.
* Exaggerated Features: Noses can appear very large, foreheads can appear very small, and ears can seem to disappear.
* Environmental Portraits: Often used to include a large portion of the background, placing the subject within their environment. Less flattering for close-up portraits due to distortion.
* Unnatural Look: Faces may appear stretched and unnatural.
* "Normal" Lenses (e.g., 50mm):
* More Natural: Provide a field of view that is close to how the human eye sees, resulting in a more natural representation of the face.
* Minimal Distortion: Distortion is minimal compared to wide-angle lenses.
* Versatile: Can be used for a variety of portrait styles, from headshots to full-body portraits.
* Good Starting Point: A good starting point for learning portraiture because it doesn't introduce extreme distortion.
* Short Telephoto Lenses (e.g., 85mm):
* Slight Compression: Starts to compress the perspective slightly, making features appear a bit closer together.
* Flattering: Considered by many to be a very flattering focal length for portraits because it offers a good balance of minimal distortion and a slight softening effect.
* Good Background Blur (Bokeh): Easier to achieve a shallow depth of field, blurring the background and isolating the subject.
* Medium Telephoto Lenses (e.g., 100mm-135mm):
* Increased Compression: Compresses perspective more noticeably than 85mm.
* Smoother Appearance: Facial features appear smoother and more refined.
* Separation: Excellent for separating the subject from the background due to the shallow depth of field possible.
* Less Intrusive: Allows you to be further away from the subject, which can make them feel more comfortable.
* Long Telephoto Lenses (e.g., 200mm+):
* Strong Compression: Compresses perspective significantly.
* "Stacked" Appearance: Can make features appear stacked on top of each other, almost like a flat plane.
* Background Blurring: Creates very shallow depth of field and highly blurred backgrounds.
* Requires Distance: Requires significant distance from the subject.
* More "Impersonal": The distance can make the portrait feel less intimate.
Distance Matters Too
It's crucial to understand that the focal length is only one part of the equation. The distance between the camera and the subject is equally important.
* To maintain the same framing (e.g., a head-and-shoulders shot) while changing the focal length, you need to adjust your distance.
* Moving closer with a wide-angle lens intensifies the distortion.
* Moving further away with a telephoto lens increases the compression.
Examples
* Nose Size: In a portrait taken with a 24mm lens very close to the subject, the nose will likely appear much larger than it does in real life. In contrast, with a 200mm lens at a greater distance, the nose will appear more proportional and less prominent.
* Face Shape: Wide-angle lenses can make faces appear rounder and wider, while telephoto lenses can make them appear thinner and more oval.
Choosing the Right Focal Length
The best focal length for a portrait depends on several factors:
* Desired Look: What kind of look are you trying to achieve? Natural? Dramatic? Soft and flattering?
* Subject's Features: Consider the subject's facial features. Someone with a prominent nose might benefit from a longer focal length. Someone with a very narrow face might look better with a slightly wider lens (but careful to avoid distortion).
* Background: How much of the background do you want to include? A wide-angle lens is necessary for environmental portraits, while a telephoto lens is ideal for blurring the background.
* Your Shooting Style: Do you prefer to interact closely with your subject, or do you prefer to maintain a distance?
Experimentation is Key
The best way to understand the effects of focal length on portraiture is to experiment! Take the same portrait with different focal lengths and see how the face changes. Pay attention to the distance between you and your subject. You'll quickly learn which focal lengths work best for different situations and desired aesthetics.