Aperture and Depth of Field Explained for Galaxy Phones

Aperture is the opening in your camera’s lens that light passes through to reach the image sensor. Its size decides both how much light gets in and the depth of field, which is how much of your photo is sharp from front to back. On most cameras you can change the size of the opening, but on a Samsung Galaxy each lens has a fixed aperture, which is why you won’t find an aperture setting in Pro mode.

This guide explains what aperture and f-numbers are, why your Galaxy’s aperture is fixed, and how you can still control depth of field and get that blurred background.

What is aperture?

Most camera lenses contain an iris diaphragm: a ring of thin blades that forms an adjustable opening, much like the iris in your eye. The hole in the middle is the aperture. The larger it is, the more light gets through and the shallower the depth of field; the smaller it is, the less light and the deeper the depth of field.

The size of the aperture is given as an f-number, or f-stop: the focal length of the lens divided by the diameter of the opening. That’s why the numbers seem backwards, with f/1.4 a relatively large aperture and f/16 a small one. The standard series is f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11 and f/16, and each step lets in half as much light as the one before, which is one stop.

Galaxy phone apertures, lens by lens

Since it has the largest aperture (typically) and is in front of the biggest sensor, the main camera will perform best in low light and require the least amount of ISO. Telephoto cameras, on the other hand, have smaller apertures and are in front of smaller sensors, so they’ll need more light and will introduce noise earlier on as light diminishes.

Why Galaxy phone lenses have a fixed aperture

Diffraction, the tendency of light to spread out a little as it passes through the edges of an aperture, limits how sharp a camera can be, and that effect gets more pronounced the smaller the aperture. That’s one reason phone cameras almost always have fixed apertures, along with the simple fact that there’s not much room in a phone’s camera module for all of the blades and a motor to vary the aperture size. And since phone camera lenses are so short (actual focal lengths are measured in just a few millimetres), their apertures at maximum opening aren’t very big to begin with, so there’s a limit to how much they can be reduced without depriving their already-small sensors of too much light.

There have been exceptions. Samsung’s Galaxy S9 and S9+, followed by the Note9, the S10 and S10+ and the Note10, had main cameras that could switch between f/1.5 and f/2.4, opening up in dark scenes and closing down a little in bright ones. Samsung went back to a fixed f/1.8 main camera, with a larger sensor, on the Galaxy S20 in 2020. It never officially said why; reports pointed to the bigger new sensors, sharpness, and the cost and space of the mechanism.

What is depth of field?

Depth of field refers to the area in front of and behind the area you have focused on that is acceptably sharp. Depth of field can be shallow (your subject will be sharp, but the background will be blurred out) or deep (everything from the flowers in the foreground to the mountains in the background will be sharp).

Depth of field is affected by four things: your aperture setting, the focal length of your lens, your distance from your subject and the size of your camera’s sensor. In general, the wider your aperture, the longer your lens, the closer you are to your subject and the bigger your sensor, the shallower your depth of field will be. Numerical values for what we consider to be "acceptably sharp" are given in our circle of confusion guide.

Why phone photos have so much in focus

Phone sensors are small, and smaller sensors mean shorter real focal lengths, which gives a deeper depth of field: more of the image is in focus, even with bright lenses. We calculated that the f/1.7 lens on the Galaxy S25 Ultra’s 1/1.3-inch main camera gives a similar depth of field to f/6 on a full-frame camera framing the subject the same way. The Galaxy S26 Ultra’s f/1.4 main camera is the equivalent of around f/5, while the f/1.8 main cameras of the Galaxy S25, S26, A56 and A57, with their smaller 1/1.56-inch sensors, are around f/7.6.

A deeper depth of field isn’t always a bad thing. It means everything from the foreground to the background is in focus in landscapes, cityscapes, group shots and documents. But it can be frustrating with portraits, where the soft background you’d get from a DSLR or mirrorless camera is missing, and that’s where the tips below come in.

How to blur the background on a Galaxy

• The closer you get to your subject, the shallower the depth of field will be (which is why close-up shots of flowers and food often have blurry backgrounds, even when shot on a phone). That said, all lenses have a minimum focus distance, so if your phone can’t focus on something, try moving back a little.
• Position your subject further away from the background. If you’re photographing a person, for example, move them a few metres away from the hedge or wall behind them. The further away the background is from your subject, the blurrier it’ll look.
• Use the 3x or 5x camera. Telephoto shots show less of the background and magnify it, which makes it look blurrier. Move further away from your subject so they’re the same size in the frame. Our telephoto lens guide covers each Galaxy's zoom cameras.
• Use Portrait mode. This cleverly works out what’s in the background and blurs it using software. You can use the Portrait effect slider to control how blurry the background is, and it doesn’t always look best cranked up all the way. See our Portrait mode guide.
• Blur the background later on. In the Gallery you may notice Background blur offered up as a suggested edit. This can add a Portrait mode-esque effect to shots of pets and people taken in Photo mode.
• Try Virtual aperture. Samsung added it to Expert RAW with the Galaxy S25 series. It simulates different aperture settings (f/1.4 to f/16, according to SamMobile), and on our Galaxy S25 Ultra with One UI 9 it’s in Expert RAW’s Labs menu. Like Portrait mode, it doesn’t change the lens’s aperture; it fakes the effect with software.

Blur in Portrait mode isn’t exactly the same as blur you’d get with a real lens. Lens blur grows gradually with distance and turns lights into soft discs, the effect called bokeh. Inspect close up before posting, as software blur can be very uniform and occasionally hair and glasses edges get clipped. Methods are compared in our blurring the background on a Samsung guide.

How to get everything sharp

With a landscape or cityscape, you’re more likely to want everything in focus from the foreground to the horizon. This should be fairly easy to accomplish on a phone. Shoot with the 1x or 0.6x lens and don’t stand too close to the nearest object. Tap to focus about a third of the way into the picture (not at the horizon). If something is really close in the foreground, consider using the Pro mode and manually setting the focus. Focus peaking can help you make sure everything from front to back is in focus. Our hyperfocal distance guide gives the distances for each Galaxy lens.

Aperture and exposure on a phone

Whereas with a larger camera you’d typically adjust the aperture, shutter speed and ISO to get the exposure you’re after, with your Galaxy you’re limited to playing around with just the latter two. So if, say, you wanted to use a slow shutter speed in bright conditions to blur a rushing waterfall, you’d need to set the ISO as low as it’ll go and consider using a neutral density (ND) filter to help cut the amount of light reaching the sensor (ND filters are basically just darkened pieces of glass that attach to the lens). Our exposure triangle guide and ISO guide explain the balance.

Frequently asked questions