Understanding Focal Length On Smartphone Cameras
If you have ever visited a website such as GSM Arena and looked up the specifications of smartphone cameras, you may have noticed that the lens specifications were preceded by measurement such as 26mm, 52mm, or 12mm next to the lens specifications. what is the focal length of a smartphone camera
This is a measurement of the focal length of the lens, which has a significant impact on the final image that is produced by your digital camera.
In this article, we’ll look at the role that focal length plays in photography and how it affects the photos you take with your camera.
However, before we can discuss focal length on smartphone cameras, we must first understand what it is and how it functions in traditional photography. You will be better equipped to understand how it works on smartphones if you have a solid understanding of the technology.
What does focal length mean?-What is focal length in photography?
A camera’s focal length is measured in millimetres (mm) and refers to the distance between the camera’s image sensor and the point in the lens where light converges and focuses the image inside the lens.
Let’s break that down a little more…
When light travels, it does so in a straight line with no interruptions. Put in front of it, a single convex lens will cause all of the parallel light rays to converge and bend towards a single point, which is known as the focal point.
Things, on the other hand, aren’t quite so straightforward in a standard camera lens. It takes more time to get to the focal point because light must pass through an array of concave and convex lenses that converge and diverge instead of just one single lens.
When the image is in focus, the focal length is the distance between the point where the light converges in the lens and the image sensor on the other end of the camera.
For example, if the focal length of a lens on a digital SLR camera is stated to be 28 millimetres, this means that at its sharpest focus, light converges in the lens 28 millimetres above the sensor.
Because of the 50mm focal length, when the light converges at 50 millimetres from the sensor, the image is sharply focused 50 millimetres away from the sensor.
Why does the focal length matter?– focal length of phone camera
The focal length of a lens is important because it allows you to determine the angle-of-view (also known as field-of-view) and magnification of the lens based on its measurements.
As the focal length of the lens increases, you will see less of the surrounding scene and your subject will appear more magnified. This is ideal for portrait photography, where the focus should be on the subject rather than the surrounding scenery.
A short focal length provides you with a wide field of view, which is ideal for taking landscape photos with your camera.
So, after looking at what focal length is and how it is measured in traditional, dedicated cameras and lenses, it’s difficult to ignore the fact that something doesn’t quite add up in this situation.
If the focal length is defined as the distance between the sensor and the optical centre of the lens, it is impossible for a smartphone camera to have a lens with a focal length of 24mm, for example.
This raises an interesting question…
what is the focal length of a smartphone camera
How is focal length different in smartphones?
Because of the limited amount of real estate available on smartphones, mobile cameras are small and have small sensors when compared to the likes of a full-frame DSLR camera, for example.
which focal length is better in mobile camera?
This results in a very short physical distance between where the image is focused inside the lens and where it is captured on the sensor when the image is captured. Despite the fact that a smartphone camera advertised as having a 26mm lens actually has a focal length of 4.25mm, this is not true.
To be completely honest, 4.25mm is meaningless in the context of true photography. The focal length is calculated using the equivalent of a 35mm full-frame sensor as a starting point for comparison.
In order to account for this, you’ll notice that the focal length of the phone’s lens or lenses is expressed in terms of the equivalent of a 35mm-format sensor rather than the smartphone’s own sensor format.
What does 35mm equivalent mean?
The 35mm focal length equivalent of a lens gives you an idea of the focal length of the lens you’d need to use if you were to capture the same image with a camera that had a 35mm full-format sensor, which is a useful tool when shooting with a zoom lens.
To put it another way, if you look at the specifications of a smartphone camera and see that it has a camera with a 24mm lens, it basically means that you’d have to use the same 24mm lens on a full-frame DSLR camera, for example, to get the same shot with the same angle of view that you obtained using the phone camera.
Knowing the 35mm equivalent is important for photographers, especially those who switch lenses between cameras with different size sensors, because the focal length is affected.
The 35mm equivalent is useful for mobile photographers because it gives you a better idea of how wide or narrow the angle of view is for a given lens when shooting on the go.
Focal length and angle-of-view
For the same reason as previously stated, the focal length is closely related to what is referred to as the angle of view. The amount of the scene that is visible through the lens is what this term refers to. This measurement is expressed as a number of degrees.
You will see more of the scene if your lens has a short focal length, which means you will have a wide angle of view and will see more of it. Some ultra-wide-angle lenses have an angle of view as wide as 180 degrees, which is extremely wide for a camera lens. The fisheye effect, on the other hand, is introduced into the picture as a result of this distortion.
A long focal length means that you will have a smaller field of view and that your subject will appear magnified when you look through the camera. Instead of capturing the entire landscape with one lens, using one with a long focal length will allow you to capture only part of the landscape while capturing more of the buildings in the frame, as opposed to using two lenses with a wide angle-of-view. Take a look at the following illustration.
The greater the magnification obtained, the longer the focal length is. When you zoom out, your field of view becomes wider and your focal length becomes shorter.
What’s the typical focal length of a smartphone lens?
Because different devices have different lenses, this is a difficult question to answer. Additionally, smartphones with more than one camera are more likely to have lenses with varying focal lengths.
The typical focal length of various smartphone cameras is shown in the table below.
|Camera type||Focal length||Angle-of-view|
|Wide-angle||22mm to 30mm||~84° to ~62°|
|Telephoto||50mm to 80mm||~40° to ~25°|
|Ultrawide-angle||12mm to 18mm||~112° to ~90°|
|Periscope||103mm to 125mm||~20° to ~16°|
Single-lens smartphone cameras are commonly equipped with a wide-angle lens with an equivalent focal length of approximately 22mm to 30mm.
what is the focal length of a smartphone camera When a smartphone has more than one camera, it can be any combination of a wide-angle main camera and an ultra-wide-angle second camera, or a telephoto lens, or both? Ultra-wide-angle lenses have focal lengths that are roughly equivalent to 12mm to 18mm on a 35mm camera.
A large number of smartphones are equipped with “telephoto” lenses, which have focal lengths that are twice as long as the wide-angle lens. In today’s world, however, it is not uncommon to find smartphones equipped with cameras that have a telephoto lens with a focal length that is said to be more than twice as long as that of their wide-angle lenses.
Generally speaking, a smartphone telephoto camera with more than 2x optical zoom is referred to as a “periscope camera” or “periscope zoom lens” in most instances.
Despite the fact that it is a telephoto camera, I have listed it separately in the table above due to the way it operates in comparison to a traditional telephoto lens on a mobile phone. More information on periscope cameras can be found here.
The longer the focal length of the telephoto lens, the greater the amount of optical zoom the phone camera can achieve. This means that the picture quality is better than when using digital zoom is used.
what is the focal length of a smartphone camera
How does attaching an external lens affect a smartphone camera’s focal length?
There are many different types of smartphone camera lenses available, including telephoto, macro, ultrawide-angle, and others. These look a lot like some of the lenses found on smartphones with multiple camera capabilities.
In a similar vein, the focal lengths of the various types of add-on lenses vary. Moreover, they are within the same range of focal lengths and viewing angles as the mobile camera lenses listed in the preceding table.
Because the primary rear camera on a mobile phone is typically the one with the best mobile camera specs on that particular mobile phone, most external smartphone camera lenses are designed to be attached to the primary camera in order to take advantage of the picture quality provided by the primary camera on the phone.
The primary camera on most smartphones has a wide-angle lens with a focal length ranging from 24mm to 27mm, which is sufficient for most situations. With this camera, you can capture shots that are relatively wide and capture a significant portion of the scene.
Attaching an add-on lens to that camera will provide you with a different angle of view that corresponds to the focal length of the external lens.
Using the above example, when you attach an ultra-telephoto lens (which has a narrow angle-of-view) to a smartphone with a 26mm wide-angle camera, the smartphone’s camera will not capture a wide-angle shot, but rather one that matches the focal length of the telephoto lens.
Use caution when photographing with add-on lenses if you want to achieve the best possible results. Even though low-cost lenses are convenient for the wallet, they frequently produce images of poor quality, despite the optical capabilities of the phone’s camera.
For add-on smartphone lenses, I highly recommend Moment and Olloclip, both of which are available from Amazon. They manufacture high-quality lenses that are specifically designed for mobile photography and even mobile filmmaking applications. Of course, these aren’t the only options available. There are a variety of other options available to accommodate different phone models and budgets. what is the focal length of a smartphone camera
However, what many people are unaware of is that their smartphones are capable of producing some truly amazing photographs. It’s even possible to monetize your mobile photos by selling them online for extra cash or by printing them as works of art.
There are a plethora of websites on the internet that offer photo printing services, but one in particular that I discovered is Pictorem, which is simply amazing. They’ve been around for a long time and can print images (not just smartphone photos) on a variety of surfaces, including canvas, metal, acrylic, and wood.
If you want to print and display your photos, or if you want to give them as gifts to friends and family, you should definitely give Pictorem a shot. Very good value for money!
Not to worry if your photos aren’t quite to the point where you’d like to have them printed and displayed yet; you can get there as well. All that is required is some learning and practise.
That’s why I’ve put together a simple introductory guide that will teach you how to take beautiful mobile photos that are good enough to print and display in your home or share with friends and family.
If you’re interested in learning how to improve your smartphone photography skills, you can get the 5 Ways To Improve Your Smartphone Photography ebook by clicking on the banner above or by clicking this link. A great deal can be learned from its 22 pages of content, and it is completely free to download!!!
Focal Length and Photogrammetry
Here are some details to remember in relation to focal length and photogrammetry / Camerajar:
- PhotoModeler requires knowledge of the principal distance between the camera and lens at the time of the photos’ capture in order to solve geometry, calculate camera positions, and generate 3D coordinate points. For greater accuracy, a) calibrate the camera to determine the exact focal length/principle distance (or at the very least, use a reasonably close focal length estimate), and b) take photos with the camera set at the same focal length (zoom setting) as when the camera was calibrated, if using a zoom lens (for repeatability, use the widest angle or fully zoomed).
- Both the format size and the focal length are critical considerations. Being able to identify the focal length alone is insufficient.
To calculate the focal length/principle distance and the format size, PhotoModeler provides four different methods. These are: a) Camera Calibration, b) the quick Approximate Camera method that uses the images’ EXIF header, c) the Inverse Camera method (for projects that use photos from an unknown source), and d) Field and Auto Calibration, among other things (which is camera calibration executed at the same time as the modelling project). For the most consistent and accurate project results, calibrate your camera and then use it at the same focal length that you calibrated it at throughout the entire project.
Is there a relationship between focusing and focal length?
We mentioned earlier that focal length is related to the distance between the two points of focus. When a camera is focused at infinity, the focal length is the distance between the lens and the subject. In photogrammetry, we are interested in the internal geometry of the camera at the time of the photographs; therefore, the principal distance is the distance that we want to know precisely in photogrammetry.
The answer is yes, focusing a lens changes the principal distance between the two points.
All lenses have a focal length that is stated or specified on the packaging (or range of values for a zoom lens). When the lens is focused at infinity, the printed number represents its nominal length, which is the principal distance between the two points on the lens. The principal distance changes as you bring your attention to objects that are closer to the camera. At the time of the shot, a 50mm lens focused on an object a few feet away might have a principal distance of 55mm lens, for example. When using a macro setting (a lens setting that allows you to focus on very close, very small objects, such as those measuring less than 5 inches in diameter), this is the most extreme example. Even though a lens has a nominal focal length of 50mm (and, therefore, a principal distance of 50mm when focused at infinity), it may have a principal distance of 100mm when focused at a few inches or less! This is why it is beneficial to calibrate a camera at the distance at which you will be working when working in photogrammetry (where precise geometry is required).
The ability to calibrate a camera (which solves the principal distance) at one focus and execute your photogrammetric project at another focus exists to a certain extent. The actual discrepancy that is acceptable is determined by your accuracy requirements as well as how much the focus shifts over time. Generally speaking, a calibration performed at a focus distance of 2m/6ft is acceptable for projects up to infinite focus (again, depending on the accuracy requirements), but it may not be acceptable for a project where the focus distance was 50cm/20in (or greater).
Though the advantages of using focus (i.e. crisp targets and distinct features) with subtle effects on principal distance/focal length outweigh the advantages of maintaining constant focus and principal distance in many cases (i.e. potentially causing blur in some photos taken at a different distance).
Focal Length and Photogrammetry are two terms that are used in photography.
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