Eddie Nguyen
Every exposure is three settings agreeing on one thing: how much light ends up on the sensor. That’s why people draw it as a triangle. Move one corner and you have to move another to keep the same brightness.
The brightness part is easy. The useful part is that each setting has a side effect you can see in the picture. Pick the side effects you want first, and the brightness sorts itself out.
Aperture: how wide the lens opens
The f-number is the size of the hole in the lens. A smaller number means a bigger opening and more light. The full stops go f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, and every step halves the light.
The side effect is depth of field: how much of the scene is sharp. At f/2.8 on my Sigma 24–70mm at the long end, the background melts away behind a face. At f/8 a whole desk is sharp from front to back.
- Talking head: f/2.8, so the room behind me goes soft.
- Desk overhead: f/5.6 to f/8, because every cable and keycap should be in focus.
Shutter speed: how long the sensor looks
For photos, shutter speed decides whether movement freezes or blurs. 1/1000 stops a jump in the air. 1/30 turns a passing scooter into a streak.
For video there’s a rule that makes it simple. The 180-degree rule says your shutter should be about one over twice your frame rate:
| Frame rate | Shutter |
|---|---|
| 24p or 25p | 1/50 |
| 50p | 1/100 |
| 60p | 1/120 or 1/125 |
That much blur per frame is what our eyes read as natural motion. A much faster shutter makes movement look choppy, which can be a look for action or rain. A slower one smears everything.
In Vietnam the mains power runs at 50 Hz, so most indoor lights flicker 100 times a second. Shoot at 1/50 or 1/100 and the flicker disappears. That’s why I shoot 25p and 50p at home instead of 24p and 60p.
ISO: how much the camera amplifies
ISO doesn’t add light. It turns up the signal the sensor already caught, and turns up the noise with it. Double the ISO and the picture gets one stop brighter, and a little grainier.
Modern sensors are clean much higher than they used to be. I’m happy up to around ISO 3200 to 6400 on my A7C II for YouTube. Past that I’d rather add a light than push the ISO again.
If you shoot S-Log3, the lowest ISO you can pick goes up. More on that in how I shoot S-Log3.
The order I set them in
Shutter first. For video it’s already decided by the frame rate: 25p means 1/50.
Aperture second, for the look. How much of the scene should be sharp?
ISO last, to fill the gap until the brightness is right.
Still too bright? Use an ND filter. Don’t speed up the shutter, or you break the motion blur you just set. A variable ND covering two to five stops handles most daylight.
Quick fixes
- Daylight video is too bright even at the lowest ISO: ND filter.
- The background is too sharp: open the aperture (lower f-number) and move the person further from the wall.
- The image is noisy: add light before you raise the ISO. A window counts.
- The lights flicker: set the shutter to 1/50 or 1/100.
That’s the whole triangle. Learn which side effect lives in which corner, and you’ll stop thinking about stops at all.