What is the focal length on your typical cell phone camera?

Question

I know cell phone cameras are generally wide angle, which makes sense because people wanna go out to dinner, or a show, or at the park with their kids, and they want to get the whole scene. And even though digital zoom is horrible...if anyone needs to get closer, they zoom.

I am not in a rush to get a wide angle lens for my DSLR just yet. For now, I believe that I can get away with just using my phone for wide shots. And yes, I know it is not necessarily the same because the available aperture and things like this.

However, I recently learned that even smartphone pictures may have EXIF metadata in them. For my phone's camera, it gave me a focal length of 5mm. Now I understand the sensor size on the cameras are much smaller, so how do I calculate the 35mm-equivalent?

Does anyone know what the focal lengths are on cell phones?

Answer 1

The actual focal length of the lens is usually measured along with the crop factor of the sensor. Cell phones, needless to say, have a huge crop factor. For example, the Samsung Galaxy SIII and iPhone 4 are a 7.6x crop. So, if you have a 5mm lens on one of those, you're looking at an equivalent full frame focal length of 38mm. That's wide, but not that wide... you could get far wider on any dSLR.

If you want to play with some comparisons, you can look for a camera sensor size comparison site to match up your phone and dSLR. I would expect the phone lenses to usually fall somewhere around 30-50mm in effective field of view versus a full frame dSLR.

Answer 2

Focal length does not change with sensor sizes - what actually changes is the field of view:

FOV [°] = 2 * arctan ( d [mm] / (2 * f [mm]) )

FOV is our field of view in degrees, d is one of the dimensions of the sensor (for diagonal, it is d = √(h² + w²) ) and f is the focal length in millimeters.

In very simple terms, a smaller sensors sees a smaller portion of the lens's projection - e.g. a APS-C sensor does not fill out a 35mm lens's image circle, so it cannot see the outer portions (which relate to the outer regions of the frame) and therefore, the field of view is narrower than it would be with a full frame camera.

When we talk about crop-factors, what we really are talking about is the change in field of view by a smaller sensor: The reference is a full frame sensor, which is 36*24mm. Therefore, a 10mm lens on an APS-C camera is still a 10mm lens - it just happens that it offers the same FOV as a 15mm lens would on a full frame camera.

The same of course is true for smartphones - unfortunately, the smartphone market is constantly and rapidly changing, and manufacturers usually do not state focal length or sensor size in their marketing texts, so research is needed on a per-phone-basis (or so I think).

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A (at this moment) recent iPhone X offers an equivalent-to-28mm lens and an equivalent-to-52mm lens, the Samsung Galaxy S9+ offers 26/52mm, the OnePlus 6 offers 25mm, the Huawei P20 offers 27mm/80mm, the Nokia 6.1 offers 27mm,...

So it seems we can conclude that 26-28mm (equivalent) are a standard in Q3/2018.