A lens's focal length determines both the field of view and the perspective of an image. Wide-angle lenses (under about 35mm on full-frame) capture expansive scenes and emphasize depth; normal lenses around 50mm approximate how the human eye sees; and telephoto lenses (above about 70mm) compress space and bring distant subjects closer. Photographers choose between prime lenses, fixed focal lengths often prized for sharpness, wider maximum apertures, and lighter weight, and zoom lenses, which offer variable focal lengths for flexibility without changing lenses. The popular "nifty fifty," an affordable 50mm f/1.8 prime, is a classic first lens for many photographers. The aesthetic quality of out-of-focus areas, known as bokeh, is influenced by aperture blade design (more blades create rounder bokeh) and by using longer focal lengths and wider apertures.
Sensor size also shapes the image. Full-frame sensors match the 35mm film standard, while crop sensors (such as APS-C or Micro Four Thirds) are smaller and apply a crop factor, typically 1.5x for APS-C, to the focal length. A 50mm lens on an APS-C body behaves like roughly a 75mm lens on full-frame. Larger sensors generally offer better low-light performance, shallower depth of field, and wider dynamic range, which is why medium format sensors — even larger than full-frame — are favored in studio, fashion, and fine art work. Modern camera trends favor mirrorless systems over DSLRs because they eliminate the mirror and use electronic viewfinders, allowing for lighter, quieter bodies.
Composition is the arrangement of elements within the frame. The rule of thirds divides the image into a 3x3 grid and places important subjects at the intersections; leading lines draw the eye into the scene; framing uses elements within the scene to surround the subject; and the golden ratio (phi ≈ 1.618), often visualized as a golden spiral, offers a pleasing proportional guide. Other techniques include filling the frame by getting close, using odd numbers of subjects for dynamic balance, and layering foreground, middleground, and background to create depth. Perspective, the camera's physical position, also tells a story: shooting at eye level creates intimacy, a high angle can diminish a subject, and a low angle can make a subject appear powerful. Symmetrical compositions feel stable and formal, while negative space gives subjects room to breathe.