Soft Lite Studios

The Ultimate Imaging Experience

EXPLORE: New Perspectives, New Techniques, New Skills

ENRICH: Your Vision, Your Knowledge, Your Passion

ENGAGE: In Bigger Ideas, In Bigger Productions, In Bigger Networks

Completely Mechanical · Week 3 of 13

Aperture & Depth of Field

The second control opens and closes an iris inside the lens — setting how much light gets through, and quietly deciding what's sharp and what melts away.

  • With Alexandra Anais & Tim Neumann
  • Commanding Exposure · Amount
  • Mirrorless-First · DSLR · SLR · Film
  • 7 min read

Last week the shutter gave us control over time. This week we open the second control on the path of light — the aperture — and it governs the other half of exposure: not how long light lands, but how much of it gets through at all. It's an iris of overlapping blades, and you already know the surprise from Week 1: it lives inside the lens, not the camera body. This week we put it to work, and discover that the thing it really controls isn't brightness at all. It's depth.

What the Aperture Does

The aperture is a ring of thin blades that overlap into a roughly circular hole, and that hole can grow or shrink. Open it wide and a flood of light pours through; close it down and only a trickle gets past. That's the whole mechanism — a variable opening, sitting in the lens, metering light by quantity the way the shutter metered it by time. Together those two controls set your exposure: time and amount, the pair we flagged last week.

The f-Number That Runs Backward

Aperture is measured in f-stops, written f/2, f/5.6, f/11, and so on — and here's the part that trips up every beginner: the smaller the number, the bigger the opening. f/2 is wide open and bright; f/16 is a pinhole. It feels backward because it's a ratio, not a width — the f-number is the focal length divided by the opening, so a bigger denominator means a smaller hole. You don't have to love the math. You do have to memorize the direction: small number, big hole, lots of light.

And the doublings are back. The full stops — f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16 — each halve the light of the one before, exactly as shutter speeds halve time. Same rhythm, different control. Once you feel it on the shutter, you already feel it here.

Depth of Field: The Real Reason You Care

If aperture only changed brightness, you'd barely think about it — you'd just trade it against shutter speed. What makes it a creative control is the side effect: depth of field, the slice of the scene that's acceptably sharp from front to back.

  • Wide aperture (small f-number, like f/2) — a shallow slice of focus. Your subject is razor-sharp and the background melts into soft blur. This is how portraits lift a face off its surroundings.
  • Narrow aperture (big f-number, like f/16) — a deep slice. Everything from the near foreground to the horizon stays sharp. This is how landscapes hold detail front to back.

Aperture is the main lever on depth of field, but two other things push it: longer lenses and closer subjects both shrink the sharp slice further. For this week, change only the aperture and watch the background harden or dissolve.

How Aperture Works Across Cameras

Same iris, same f-stops — but how you set it, and whether you can see its effect before you shoot, differs by body.

Mirrorless Set it with a command dial, and the electronic viewfinder previews depth of field live — open up and watch the background blur in real time as you turn. The most immediate way there is to learn aperture.
DSLR / SLR The optical finder almost always shows the scene wide open, so you don't see the true depth of field until you press the depth-of-field preview button, which stops the lens down to your setting. Build the habit of using it.
Film Often an aperture ring right on the lens barrel — you set the f-stop by hand, by feel, with a satisfying click. The SLR finder still shows wide open, so depth of field is something you learn to predict rather than preview.

"So a smaller number is a bigger hole. I wrote 'SMALL = BIG' on a sticky note and stuck it to my lens. I'm not embarrassed. It's the only way it stuck."

Alexandra
Key Takeaway

Aperture sets how much light gets through — and, almost as a bonus, how much of your scene stays sharp. Wide open isolates; stopped down holds everything. You now own both halves of exposure: the shutter's time and the aperture's amount. Next week we meet the third variable — the one that decides how greedily the imaging plane drinks all that light: ISO.