Short Focal Lengths (e.g., 24mm, 35mm, sometimes even 50mm on crop sensors):
* Widens the face: Short focal lengths exaggerate the distance between features closest to the camera and those further away. This makes the nose appear larger and more prominent relative to the ears and the sides of the face. The sides of the face may seem to recede, making the face appear wider overall.
* Exaggerates perspective: The background appears further away and more compressed. Lines converging in the distance are more pronounced.
* Less flattering for most people: Generally, these are not flattering for typical portraits because they distort features in a way that isn't considered aesthetically pleasing. They can make the nose seem too big and the face too round.
* Uses: Used for environmental portraits where you want to show the subject in their surroundings and the distortion is part of the artistic expression. Also, sometimes used deliberately to create a humorous or caricatured effect.
"Normal" Focal Lengths (e.g., 50mm on full frame, 35mm on crop sensor):
* More natural perspective: This focal length approximates how we see the world with our own eyes. There's less perspective distortion compared to wider or telephoto lenses.
* Balanced proportions: Features are rendered more proportionally, without significant exaggeration or compression.
* Versatile: A good starting point for portraits and provides a good balance between subject isolation and showing some of the environment.
Long Focal Lengths (e.g., 85mm, 105mm, 135mm, 200mm):
* Compresses the face: Longer focal lengths reduce the perceived distance between features. This makes the nose appear less prominent and the face look slimmer. The distance between the foreground (subject) and the background also appears reduced.
* Creates a shallow depth of field: Easier to blur the background, isolating the subject.
* Flattering for most people: These are often preferred for portraits because they smooth out features and create a more pleasing, even rendering of the face. The compression tends to make people look more attractive, according to common aesthetic ideals.
* Reduces distortion: As you move further away to take a portrait, and use a long focal length, the amount of parallax/perspective distortion lessens.
* Less background visible: Focuses attention almost entirely on the subject.
* Requires more distance: You need more space between you and the subject to achieve the desired framing.
Key Concepts:
* Perspective Distortion: This is the apparent alteration in the size and relative position of objects as viewed from different distances. Wide-angle lenses emphasize perspective distortion, while telephoto lenses minimize it.
* Compression: Telephoto lenses compress the distance between objects, making them appear closer together than they actually are.
* Distance to Subject: Changing the focal length *and* your distance to the subject is how you achieve different effects. Simply zooming in or out will only change the size of the subject in the frame, but not the perspective distortion. To truly leverage focal length, you need to adjust your position.
Practical Implications:
* Choose a focal length that complements the subject's features: Consider whether you want to minimize a prominent nose or widen a narrow face.
* Experiment to find your preferred focal length: Try different focal lengths to see how they affect the look of your portraits.
* Don't be afraid to break the rules: While longer focal lengths are generally considered more flattering, sometimes a wider lens can be used effectively for a more dramatic or environmental portrait.
* Crop Sensor Considerations: Remember that the equivalent focal length on a crop sensor camera is longer than the marked focal length on the lens (e.g., a 50mm lens on a 1.6x crop sensor is equivalent to an 80mm lens on a full-frame camera).
In Summary:
| Focal Length | Face Shape Effect | Other Effects | Common Use |
|--------------|-------------------------------------------------------|---------------------------------------------------------------|--------------------------------------------------------|
| Short (24-35mm) | Widens face, exaggerates nose | Exaggerated perspective, more background visible | Environmental portraits, artistic/humorous effects |
| Normal (50mm) | More natural proportions | Balanced perspective and subject isolation | General portraits, versatile choice |
| Long (85mm+) | Compresses face, makes nose less prominent, slims face | Shallow depth of field, compresses background, flattering | Flattering portraits, isolating the subject |
By understanding how focal length affects the shape of the face, you can choose the right lens to create portraits that are both technically sound and aesthetically pleasing. Remember to experiment and find what works best for your style and your subjects.