Most photographers are not aware of what they could be doing with different focal lengths.
They use focal length to crop their photographs.
They simply zoom back-and-forth.
That's useful, but they could be doing more.
Are they stupid?
They're not aware of focal length because it's hard to know what focal length you're using, these days.
Before the advent of the great zoom lenses we use today, a photographer would reach for, say, a 24mm lens or a 100mm lens.
He or she would, obviously, know what focal length was being used.
Later, looking at the results, the photographer would see the differences between the same scene photographed with a 24mm focal length versus a 100mm focal length.
Today, we're less aware of the focal length.
As mentioned, zoom lenses are great for selecting what's in the frame.
• You can zoom in to bring something closer.
• You can zoom out to see more of the entire scene.
But, you can also play with volume and space.
• Wide-angle focal lengths:
1) Show volume.
2) Push backgrounds far away.
• Telephoto focal lengths:
1) Flatten subjects.
2) Bring foregrounds, subjects, and background. closer together.
Do a headshot (face only) with the following three focal lengths.
Have something in the background, that's visible in the frame.
The person's face will be distorted.
On a digital SLR cameras, a common wide-angel focal length is 18mm.
On a point-and-shoot camera, zoom the lens to the point at which it's most wide angle, such as 8mm.
A medium focal length is best for headshots.
On digital SLR cameras, use a focal length of 55mm, 75mm, or 85mm, or thereabouts.
On a point-and-shoot camera, zoom the lens back-and-forth, to gain a sense of when the zoom is in the middle of its range.
The person's face will be flattened.
On digital SLR cameras, use a focal length of 200mm, or thereabouts, if you have a zoom lens that goes that far.
On a point-and-shoot camera, zoom the lens until it's at the most telephoto position.
As you go from wide-angle to telephoto focal lengths, you'll have to move further from your subject.
Try to place the model in the frame in the same way, even though the focal lengths are changing dramatically.
Compare your three photographs side-by-side.