Camera lenses explained: focal length, aperture and real-world use

Start with the picture, not the number

A lens does more than make a subject look nearer or farther away. Focal length changes how much of the scene enters the frame; camera position controls perspective; aperture affects light and depth of field. I choose a lens by asking what the image must communicate, how much room I have and how naturally the subject should relate to the background.

Prime, zoom, wide, normal, telephoto and macro

A prime has one focal length, such as 35mm, 50mm or 85mm. It often offers a wide aperture and encourages deliberate camera placement. A zoom covers a range such as 16–35mm, 24–70mm or 70–200mm and is valuable when moments change quickly. Wide lenses show space, normal lenses feel familiar, telephotos isolate, and macro lenses reveal fine detail.

Aperture and depth of field

A smaller f-number such as f/1.8 admits more light and can produce shallow focus; f/8 admits less light and usually keeps more of the scene sharp. Aperture is not a quality score. A portrait may benefit from separation, while an interior or family group needs enough depth for important details and faces to remain clear.

10mm and 12mm

On full frame these are specialist ultra-wide views. They can reveal a tight room or dramatic architecture, but people near the edges may stretch. I use them selectively, keep the camera level when lines matter and avoid placing faces near distorted edges. They suit property work and unusual video perspectives, not every room.

16mm, 20mm and 24mm

Sixteen millimetres works for architecture, dance-floor energy, gimbal movement and environmental storytelling. Twenty millimetres is slightly more controlled. Twenty-four millimetres is a practical wide view for a bride in a room, a team at work or an interior without making the scene feel unnaturally distant.

16–35mm and 24–70mm zooms

A 16–35mm zoom moves from a full-room view to a natural documentary wide and is useful for homes, venues and stabilized video. A 24–70mm travels from environmental views to short-telephoto portraits, making it efficient for events and commercial work. The discipline is to select a focal length intentionally rather than leaving every frame at the widest setting.

35mm, 50mm and 85mm

A 35mm places a person inside the story and works well indoors, for documentary weddings and handheld film. A 50mm is balanced for portraits, details and everyday scenes. An 85mm gives a comfortable portrait distance and clean background separation, especially outdoors or in larger venues; it can feel restrictive in a small home.

70–200mm

This zoom is valuable for ceremonies, stages, candid reactions and portraits with simplified backgrounds. It lets the team stay outside intimate moments. At longer focal lengths, support, shutter speed and focus accuracy matter more. It is usually an outdoor or large-venue lens rather than a tight-room solution.

90mm or 100mm macro

A macro lens focuses close enough for rings, jewellery, food, texture and product details to fill the frame. It can also make a strong portrait. At close distance the depth of field becomes extremely thin, so precise focus, controlled light and sometimes a tripod are essential.

Full frame, crop sensors and my practical rule

A 35mm lens on APS-C frames more like roughly 50mm on full frame; recommendations must therefore name the format. For interiors I begin around 16–24mm, for environmental portraits and film around 24–35mm, for natural portraits 50mm or 85mm, for distant moments 70–200mm, and for fine details macro. The right lens serves the story without calling attention to itself.