Simulator

AI generated demo image

Focal length and perspective

Focal length decides how much of the scene fits in the frame. Perspective, how big near things look next to far things, is decided by where the camera stands. Long lenses seem to "compress" space only because you have to stand further back to use them.

• Focal length

  The distance in millimetres from the lens's optical centre to the sensor when focused at infinity. Longer focal lengths magnify more and see a narrower slice of the scene.

• Field of view

  On a full-frame camera, 24 mm sees about 74° across, 50 mm about 40°, and 135 mm only about 15°. The badge on the picture gives the angle for the length you pick.

• Perspective compression

  With the subject kept the same size, a long lens means a distant camera. Subject and background are then at similar distances from you, so the background looks large and close behind the subject.

• Wide-angle expansion

  Up close with a wide lens, a few metres make a big difference in distance, so near objects loom large, the background shrinks away, and space feels deep and dramatic.

• Zooming from one spot

  If you stand still and only zoom, nothing about the perspective changes; the long lens just crops the wide picture. That is exactly what the simulator above does.

• The dolly zoom

  Moving the camera while zooming to keep the subject the same size makes the background swell or shrink behind it. Filmmakers use it for moments of shock or vertigo.

• Faces and focal length

  The same rule explains why portraits use 85 mm to 135 mm: from further away, noses and ears sit at similar distances, so features look natural rather than stretched.