Quick Fix Summary
Hit the Aperture (A/Av/A+) button and spin the main dial—no extra steps. Let go when you’ve nailed the setting.
What’s going on here?
Aperture’s the gatekeeper: it decides how much light hits the sensor and how much of your scene stays sharp. In video mode, it behaves almost exactly like it does in photo mode on most DSLRs and mirrorless cameras. The lens iris opens or closes, letting in more or less light. That changes both exposure and depth of field—how much of your shot stays crisp versus melting into soft blur. We measure aperture in f-stops: f/2.8 lets in way more light than f/16, for example.
Let’s do this step by step
- Pick the right mode first
- Power up the camera, then spin the Mode Dial (usually on top) to M (Manual) or A/Av (Aperture Priority).
- In M mode you’re the boss of aperture, shutter speed, and ISO. In A/Av mode the camera handles shutter and ISO while you dial in the aperture.
- Grab the Aperture button
- Find the Aperture (A/Av/A+) button on the back—often marked “A+” or “+/-”.
- Hold it down. This temporarily hands the main dial’s job over to aperture control instead of shutter speed.
- Spin the main dial
- While the Aperture button is pressed, turn the top-mounted Main Dial (the same one you’d use for shutter speed in photo mode).
- Watch the viewfinder or LCD—your aperture value (say, f/4.0 or f/5.6) updates in real time.
- Release the button once the number looks right.
- Double-check exposure and focus
- Glance at the exposure meter in the viewfinder or on screen. You want it balanced—not washed out, not too dark.
- If your camera shows a histogram, use it to confirm exposure isn’t clipping highlights or crushing shadows.
Still not working?
- Update the firmware: An old firmware build can lock out manual aperture in video mode. Grab the latest update from the maker’s site—Nikon USA Support or Canon Support are good places to start.
- Try a different lens: Some older or third-party glass won’t talk to the camera’s aperture motor. Swap in a native or officially supported lens and try again.
- Set aperture in the menu: On certain mirrorless models (Sony, Fujifilm, etc.), you can jump straight to aperture in Shooting Mode → Manual Video → Aperture without touching the dial at all.
Keep future shoots smooth
- Grab a fast SD card: Video files are big. A UHS-II card rated at least 90 MB/s keeps recording from stuttering mid-take. Check your manual for exact recommendations.
- Shoot when the light’s kind: Aperture shapes both depth of field and exposure. In dim spaces, a wide aperture (f/1.8) helps, but watch out—too shallow and your subject might blur out of focus entirely.
- Lock things down before you roll: Once aperture is set, flip on the mode-dial switch lock if your camera has one. That stops accidental mode changes while you’re rolling.
- Watch heat and power: Long takes heat up the body and drain the battery. Toss on an external pack and pause every 20–30 minutes to let the camera cool.
According to Apple Support, overheating can throttle performance in cameras with weak thermal design. The B&H Photo Video guide (2025) suggests f/2.8–f/5.6 for a cinematic look in most indoor and outdoor scenes.
