Sony a6400 Background Blur: Aperture, Distance and Lenses

To blur the background on the Sony a6400, set the lowest f-number your lens allows, zoom in or use a longer lens, get close to your subject, and put as much distance as you can between your subject and whatever is behind them. On the 16-50mm kit lens that means f/3.5 at the wide end or f/5.6 at 50mm, and the distance part often does more of the work than the settings.

What controls background blur on the a6400

A blurry background comes from shallow depth of field. The soft, out-of-focus look you get behind the subject is called bokeh.

Four things decide how much of it you get: aperture, focal length, distance, and sensor size. You choose the first three every time you shoot. The fourth is fixed by the camera.

The a6400 uses a 24.2MP APS-C sensor. Digital Camera World notes that larger sensors translate into more bokeh, and puts the a6400's sensor at about 2.8 times the surface area of the one-inch sensor in the Sony RX100 VII. That gives you a real head start over a compact camera or a phone. If you are weighing sensor sizes for a future camera, the guide to Sony APS-C vs full frame cameras covers that choice.

Aperture: use the lowest f-number

The f-number sets how wide the lens opening is. A lower number means a wider opening and a softer background. A higher number keeps more of the scene sharp.

Use a shooting mode that lets you pick the aperture yourself, such as aperture priority or manual, and turn the dial until the number stops going down. That is your lens wide open.

On the Sony SELP1650 PZ 16-50mm f/3.5-5.6 OSS kit lens, Imaging Resource lists the aperture range as f/3.5 to f/22 at the wide end and f/5.6 to f/36 at the telephoto end. The widest opening you can get changes as you zoom.

Focal length: zoom in and step back

A longer focal length makes the background look bigger and softer behind your subject. With a zoom, turn toward the long end, then walk backward until your subject fills the frame the way you want.

On the kit lens this comes with a trade: at 50mm the widest aperture is f/5.6 instead of f/3.5. For head-and-shoulders portraits, zooming in and stepping back usually still gives a softer background than staying wide at f/3.5. Take one frame each way and compare them on the screen.

Distance: the setting that costs nothing

Two distances matter. The closer you are to your subject, the shallower the focus. The farther the background is behind your subject, the softer it gets.

• Pull people away from walls, fences and hedges. A few extra steps between them and the background makes a visible difference.
• Look for backgrounds that are far away: an open field, a street receding into the distance, trees across a park.
• For small objects, get as close as the lens will still focus, then check the background through the screen.
• Indoors, put your subject in the middle of the room rather than against a wall.

Step-by-step: a soft background with the a6400

1. Set the camera to a mode where you control the aperture.
2. Zoom toward the long end of your lens.
3. Set the lowest f-number available at that focal length.
4. Move your subject away from the background.
5. Move yourself closer to the subject, or step back only as far as you need for framing.
6. Focus on the eyes, take the shot, and zoom in on the playback image to check sharpness.

If the background is still too busy, change the background before changing gear. A plain, distant background blurs far more pleasingly than a cluttered one a few feet behind your subject.

Getting focus right when the background is soft

Shallow depth of field leaves very little room for error. If focus lands on an ear or a collar, the eyes go soft along with the background.

Stills: let Eye AF do the work

The a6400 offers real-time Eye AF and real-time tracking with AI-based subject recognition, and Photography Blog notes these start with a half-press of the shutter button rather than a custom button as on earlier models. The camera's manual summary describes a 425-point phase-detection AF system.

The default focus area is usually Wide, which picks the focus area automatically, and you can switch to Flexible Spot to choose the point yourself. For portraits, leave Eye AF to it. For objects, Flexible Spot lets you put focus exactly where you want it.

Video: use tracking

In Imaging Resource's review, regular Eye-AF was not available during video capture, while Real-Time Tracking worked even in 4K video. When you film with a wide-open aperture, use tracking on your subject's face so focus follows them as they move.

Background blur vs a blurry photo

Search terms like "why is my camera blurry" often mix up two different problems. Background blur is intentional. A soft subject is a mistake, usually from camera shake or missed focus.

The a6400 has no in-body image stabilization, and Imaging Resource warns that without a steady hand or a tripod you can end up with shaky footage. Imaging Resource's reviewer reported visible wobble in the corners of handheld vertical video shot while seated. Both kit lenses carry Sony's OSS label, which helps, but a faster shutter speed and steadier support help more.

If your subject looks soft, check the playback image at full zoom. A sharp eye with a soft background is the goal. A soft eye means focus or shake, not aperture. The guide to blurry Sony ZV-E10 photos and video covers causes and fixes that apply to the a6400 as well.

Lenses that make background blur easier

The lens matters more than any menu setting. Here are the lenses that appear in the a6400 reviews used for this guide, with what those reviews say about them.

Lens	Aperture	What the reviews note
Sony SELP1650 PZ 16-50mm f/3.5-5.6 OSS	f/3.5 wide, f/5.6 at 50mm	Compact kit lens with a 7-blade circular aperture and 9 elements in 8 groups
Sony 18-135mm f/3.5-5.6 OSS	f/3.5-5.6	Bulkier than the 16-50mm, and Digital Camera World found it sharper across the full zoom range than usual for this zoom length
Sony 70-350mm f/4.5-6.3 G OSS	f/4.5-6.3	Digital Camera World's Hillary Grigonis called it sharp and noted it is weather-sealed
FE 35mm f/2.8	f/2.8	Used by Imaging Resource in its a6400 autofocus timing test

The a6400 was sold body-only or in kits with the 16-50mm or 18-135mm, with launch prices of US$900, US$1,000 and US$1,300 respectively.

If you already have lenses, or plan to buy a faster one right away, the body on its own makes more sense.

Choosing a lens for blur

When you compare lenses for soft backgrounds, two numbers tell you most of what you need: the maximum aperture and the focal length.

• Lower maximum f-number: a lens that opens wider than the kit zoom's f/3.5 to f/5.6 gives you blur at normal portrait distances without needing a long zoom.
• Longer focal length: a telephoto zoom like the 70-350mm can still soften a distant background even at a modest aperture, as long as you leave space between subject and background.
• Fixed focal length (prime): a prime lens usually opens wider than a kit zoom at a similar size, which makes it the simplest upgrade for portraits and food.

Brand badge matters less than those two numbers for this job. Whether you look at Sony's own lenses or third-party options, check the maximum aperture, the focal length, and whether the lens is made for APS-C or full frame. The guide to the Sony E-mount camera ecosystem explains how those lens lines fit together.

If you shoot a ZV-E10 instead

Digital Camera World describes the ZV-E10 as using the same technology as the a6400, with only the external design being different. The aperture, focal length and distance advice above works the same way on both cameras. For camera-specific controls, see the guide on how to blur the background on the Sony ZV-E10.

Quick fixes when the background still looks sharp

• Check that the f-number is at the lowest value the lens offers at your current zoom.
• Zoom in further and step back to keep the same framing.
• Move the subject at least several steps away from the background.
• Get physically closer to the subject.
• Swap a cluttered background for a distant or simple one.
• If all of that is not enough with the kit lens, the next step is a lens with a wider maximum aperture.

Start with distance, then focal length, then aperture. Most soft backgrounds come from where you and your subject stand, and the a6400's APS-C sensor gives you enough to work with once those pieces line up.