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← Creative Hut LibraryPhotography basics · Aperture

Part 1 of 13 in the aperture guide

What is aperture, and what does it do?

Written by Abin Alex, Founder and Director, and Anu Joseph, Faculty, Creative Hut Academy. Reviewed 29 October 2026.

Short answer. Aperture is the opening in the lens that lets light reach the sensor. It controls two things at once: how bright the picture is, and how much of the scene looks sharp.

  • The opening sits inside the lens, formed by a ring of blades called the diaphragm.
  • A wider opening passes more light, so the picture is brighter and the sharp zone is thinner.
  • A narrower opening passes less light, so the picture is darker and the sharp zone is deeper.
  • Each full step, called a stop, doubles or halves the light.

Light that the lens has focused must pass through a round diaphragm before it is recorded on the sensor. The opening in that diaphragm is the aperture. It does the same job as the pupil of the human eye, and the diaphragm is the camera version of the iris. It blocks every ray except those that go through the opening.[1]

In photography
A portrait beside a window. At f/1.8 the face is bright and the room behind melts away. At f/8 the room becomes sharp too, but you need more light, a slower shutter speed or a higher ISO to keep the same brightness.
In cinematography
A candle-lit room. With little light, the widest opening is the only way to expose without adding lights. The DOP opens the iris fully and chooses very fast lenses.[1]
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[Lecture example slot: the eye pupil in dim and bright light, beside a lens opening wide and narrow]

Figure 1. The aperture does for the camera what the pupil does for the eye.

Questions people ask

Does a bigger aperture mean a bigger f-number?

No. A bigger opening has a smaller f-number. f/1.8 is a wider opening than f/8.

Is aperture the same as depth of field?

No. Aperture is the opening in the lens. Depth of field is the range of distances that looks sharp, and aperture is one of four things that change it.

References

  1. Creative Hut Academy (2025) Aperture. Lecture slides by Abin Alex and Anu Joseph.

All 13 questions in this guide

  1. What is aperture, and what does it do?
  2. What is a diaphragm, and how does it work?
  3. What is the difference between absolute and relative aperture?
  4. How is the f-number written, and why does a bigger number mean a smaller opening?
  5. Why does each f-stop multiply by 1.4 and not by 2?
  6. What are full, half and third stops of aperture?
  7. What is effective aperture?
  8. What is lens speed, and what does maximum aperture mean?
  9. How do I set the aperture on my camera?
  10. What is the difference between an f-stop and a T-stop?
  11. Does a smaller aperture always make a sharper picture?
  12. How does aperture affect depth of field?
  13. How do cinematographers use aperture?
Back to the guideNext: part 2
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Guide by Abin Alex and Anu Joseph, Creative Hut Academy.