Why are smartphone camera bumps so huge?

Whether it’s the new Samsung Galaxy S21 Ultra, Apple’s iPhone 12 series, or the Huawei Mate 40 Pro, camera housing bumps feel bigger than ever. In fact, the phones with the biggest camera housings usually end up taking better pictures. Slimmed phones, on the other hand, have fallen down the pecking order. Although this trend seems to be having a positive effect on photography quality, it’s not the most aesthetically pleasing trade-off, and it makes for bulkier phones.

When it comes to high-end mobile photography, it’s impossible to escape the camera bump. But why? To understand, let’s dive a little deeper into the inner workings of the smartphone camera.

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Focal length, lenses, and crop factors

Before getting into the meat of the camera bump explanation, we need to get to grips with some of the essential attributes and terms of all camera designs.

We’ll start with lenses and focal length. Every camera lens, from those in DSLRs to smartphones, focuses the incoming light at the focal point, known as convergence. This focal point is where the image sensor sits to digitally capture your image. Focal length defines the distance from the lens to the point of focus, measured in millimeters. Yet, in reality, complex layers of lenses mean that the actual length is often less than the listed one. However, the effect is the same.

Dive deeper: What is focal length in photography?

Simply put, the focal length defines the camera’s field of view and “magnification.� Longer focal lengths narrow the field of view and increase magnification. This results in a zoom effect. You can imagine it by considering how changing the focal length changes the angle of view as light is refracted through a camera lens. See the image below as an example.

Importantly, focal length affects image perspective too. There is less visible separation and distinction between foreground and background objects at longer magnifications. See the apparent distance between the trees in the image above. Remember this, as we’ll come back to it later. This nuance was the cause of much debate about OnePlus’ zoom capabilities in the past.

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The other equally important part of this equation is the “crop factor.� It is often confused with the properties of focal length. The crop factor of a camera depends on the size of the image sensor. Imagine looking through the camera lens. The lens captures an image regardless of the sensor’s size. Therefore the final image captured through the lens is cropped depending on the size of the image sensor.

Notice that a smaller image sensor has the side effect of producing a tighter crop and a narrower field of view. This creates a more zoomed-in look for full-frame images, known as focal length multiplication. This is one of the reasons you’ll find small image sensors used inside smartphone telephoto cameras. However, cropping doesn’t have the same perspective effect as a native full-frame focal length at the same magnification. The crop factor is important to understand, as it plays a factor in fields of view for both zoom and wide-angle cameras found on smartphones.

The quest for bigger sensors and longer zooms

With the concepts of focal length, magnification, and crop factor under our belt, we can turn our attention to the trend for thicker smartphone camera housings.

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The first reason for larger camera housings is the pursuit of longer-range zooms. As previously mentioned, focal length is a key component of a camera’s magnification. While complex lens structures can boost effective focal length, ultimately a greater distance between the lens and sensor is required for longer distance zooms. This requirement is the driving factor behind the use of periscope technology for very long-range zoom cameras without a huge camera bump. These extend the distance from the lens to the image sensor using mirrors to reflect light. The tendency towards longer telephoto zoom capabilities is almost certainly a factor in thicker camera bumps.

The second factor driving larger camera bumps is the desire for larger image sensors. Such sensors improve light capture and picture quality. Although sensor size relates to crop factor rather than the focal length, there are reasons why longer focal lengths may be desirable with larger sensors.

For starters, smartphones likely want to retain the same image frame and magnification as previous designs when moving to a larger sensor. Keeping the same crop factor with a larger sensor requires a longer focal length. Else you end up with a wider field of view which may not be desirable. This is more important in the context of multi-camera systems, where set magnifications are required between the ultra-wide, main, and telephoto camera setup.

Read more: Why camera sensor size is more important than more megapixels

Finally, we need to consider lens distortion, which is typically most noticeable at the edges of the lens. Increasing the sensor size and using a larger crop of the lens can result in more noticeable distortion. This is more likely to be an issue with small, wide-aperture lenses used in mobile phones. See the image below as an example.

Higher quality lenses can help here. However, these are notoriously difficult to build for compact smartphone form factors and their very wide apertures. An alternative solution is to adjust the focal length. Then the field of view falls through the lens’ quality sweet spot nearer the center, where there’s less chance of distortion. However, this again requires using a longer focal length and therefore a larger camera housing.

Likewise, consider the inverse requirements of wide-angle sensors. Larger sensors or shorter focal lengths are used to widen the crop and/or increase the field of view. This is why you’ll notice much more distortion at the edges of your wide-angle pictures.

Why are smartphone camera bumps becoming so huge?

While there’s no single explanation for the increase in camera bump thickness in recent years, there is a common theme. The trend comes down to smartphone camera designers fighting against the laws of physics to improve camera capabilities and image quality.

Related: What to expect from smartphone cameras in 2021

The desire for longer range zoom capabilities and larger image sensors to close the gap on DSLR cameras are the two biggest factors driving the trend. It’s no coincidence that smartphone cameras offering industry-leading sensor sizes, zoom capabilities, and image quality tend to have larger camera bumps. While phones offering more traditional camera capabilities can retain slimmer form factors.

Not to mention demands for bigger batteries, 5G antennas, and various other bits of technology all vying for precious space inside modern smartphones. There’s simply no other option but to build thicker phones or bigger camera bumps if you want all this technology.