Shorter Focal Lengths (e.g., 24mm, 35mm):
* Exaggerated Perspective: Short focal lengths exaggerate the relative size of objects closer to the camera. This is the *key* to the changes.
* Widened Features: The nose and chin, being closer to the camera, can appear larger and more prominent than the ears and the back of the head.
* Flattened Features (Counter-Intuitively): While the nose is bigger, the *distance* between the front of the face (nose) and the back of the head seems to be shorter. This is because the wide angle captures more of the background, making the subject feel less 'separated' from it.
* Facial Roundness: Can make a face appear rounder and wider overall.
* Increased Background Context: You capture more of the background, placing the subject more within their environment. This can be good or bad, depending on your goal.
* Less Flattering (Generally): Most people don't find this very flattering for portraits because it distorts their features in an unnatural way. However, used creatively, it can be powerful.
"Normal" Focal Lengths (e.g., 50mm):
* More Realistic Perspective: 50mm (on a full-frame camera) is often considered close to how the human eye perceives perspective.
* Balanced Proportions: Facial features appear more balanced and proportionate.
* More Natural Look: The overall image tends to look more realistic and less distorted.
* Versatile: A good starting point for portraiture, offering a balance between capturing the subject and a bit of the background.
Longer Focal Lengths (e.g., 85mm, 135mm, 200mm):
* Compressed Perspective: Longer focal lengths compress the distance between objects in the frame.
* Features Seem "Closer" Together: The nose and ears appear closer in proximity to each other.
* Slimming Effect: Faces can appear slimmer and more defined, as the widening effect of shorter lenses is absent.
* Shallower Depth of Field: Longer lenses allow for very shallow depth of field, blurring the background and isolating the subject. This is ideal for emphasizing the person and minimizing distractions.
* More Flattering (Generally): Often considered the most flattering for portraits as they provide a more proportional and refined representation of the face.
* Distant Feel: Because you're further from the subject, it can create a slightly more distant or formal feel.
Here's an analogy:
Imagine looking at someone's face close up. Your nose appears huge to you, while their ears seem far away. This is similar to a short focal length. Now imagine stepping back a few feet. Your nose doesn't seem as prominent, and their features look more balanced. This is similar to a longer focal length.
Important Considerations:
* Camera Sensor Size: The "effective" focal length changes based on the sensor size of your camera. A 50mm lens on a crop sensor camera will have a narrower field of view (more like an 80mm) than a 50mm lens on a full-frame camera. You need to factor in the crop factor.
* Distance to Subject: The focal length and the distance to the subject are linked. To keep the *size* of the subject the same in the frame, you have to move closer with a shorter focal length and further away with a longer focal length. The *distance change* is the *primary* driver of the perspective distortion.
* Personal Preference: Ultimately, the best focal length for portraiture is a matter of personal preference and the desired aesthetic. Experiment to find what works best for you.
* Subject's Face Shape: Some focal lengths are better suited for certain face shapes. For example, someone with a round face might benefit from the slimming effect of a longer focal length.
In Summary:
* Short Focal Lengths: Exaggerated perspective, widened features, increased background context. Can be unflattering, but creatively interesting.
* "Normal" Focal Lengths: Realistic perspective, balanced proportions, versatile.
* Long Focal Lengths: Compressed perspective, slimming effect, shallow depth of field, more flattering.
To understand the impact, try this:
1. Position your subject.
2. Use a zoom lens (or multiple lenses).
3. Without moving your subject, change the focal length.
4. Reframe by moving *yourself* forward or backward to keep the subject's face the same size in the viewfinder.
5. Take a picture at each focal length.
This will demonstrate the perspective changes caused by different focal lengths and distances. You'll see how the shape of the face changes, and how the background is affected. This is the best way to truly understand the effect.