|Why Not All Magnifications Are The Same|
RHYS HANAK - MARCH 15, 2019
Many consumers are surprised to learn that magnification (or “zoom”, as it is commonly referred to) is not a standardized metric across all imaging devices.
In other words, each type of imaging device (ie. smartphone, binocular, DSLR camera, etc) has a different mathematical rationale behind its magnification. This can lead to considerable confusion when consumers try to compare the magnification capabilities between different imaging devices.
By better understanding how different imaging devices calculate their magnifications, consumers can make more informed decisions when considering their next smartphone or camera product purchase.
The magnification power of binoculars is specified by a pair of numbers (ie. 8×40). The first two characters, “8x”, refer to the magnification of the binoculars—or how many times closer you are to your target. The second two characters, “40”, refer to the aperture size of the binoculars.
Rest assured that aperture size still affects resolution, even in binoculars. A pair of 8×8 binoculars will be very small, but the image that you see—though 8 times closer to your target—may be dark and blurry, due to the small aperture size.
DSLR (Full Frame) Cameras
It’s important to recognize that a new kind of magnification notation comes into play with DSLR camera “lens labels”. For example, a DSLR lens labeled “14-200mm, f2.8” means that the lens has a focal length that can be changed from 14mm to 200mm and an f-number of 2.8.
We discuss the importance of f-numbers in angular resolution in our previous article, Pushing the Boundaries of Smartphone Camera technology.
It is this change in focal length—from 14mm to 200mm—that provides us with a second, “new” definition of zoom. To illustrate this second concept of zoom, let’s compare two cameras.
Camera A has a lens of 14mm to 200mm, f2.8. Since 200 mm / 14mm = 14, this camera has a 14X optical zoom.
Camera B has a lens of 200-800mm, f2.8. Since 800mm / 200mm = 4, this camera has a 4X optical zoom.
But despite Camera A technically having a larger optical zoom than Camera B, Camera B would boast a much more zoomed image—as Camera B’s final focal length value is much larger than Camera A’s.
With this example, it becomes quite clear that optical zooms in DSLR cameras are relative, based on the camera’s focal length values. So what do we do?
A helpful way to accurately comparing DSLR camera magnifications is to use binocular magnifications (ie. 50mm = 1X, 100mm = 2X, and so on). In this case, Camera A would have a 4X binocular zoom and Camera B would have an 8X binocular zoom.
With this rule-of-thumb, we can quickly surmise that Camera B provides more magnification than Camera A.
Point And Shoot Cameras
Point and shoot cameras use much smaller sensors in comparison to DSLR’s. As such, their lens labels often look slightly different.
For example, take this common point and shoot camera label: “4.3-151mm, 1:3.4-6.9”.
Just like with DSLRs, the first set of numbers refer to the focal length that the camera can change between. The second set of numbers refer to the camera’s f-number—which you can see is actually two numbers.
Using the aforementioned example, a point and shoot camera with a lens label of 4.3-151mm would result in a whopping 35X of optical zoom (since 151mm / 4.3mm = 35). If we convert these focal lengths to their 35mm equivalents, we get numbers around 25-850mm. This focal length would present a tremendous amount of zoom.
But despite this point and shoot cameras substantial magnification power, its resolution leaves something to be desired. That’s because the 4.3mm focal length of the camera would have an f-number of 3.4, while the 151mm focal length of the camera would have an f-number of 6.9.
In comparison to the f2.8 number DSLR example used above, this point and shoot would provide significantly less image resolution—thanks to its 6.9 f-number.
Because of this lacklustre resolution, the extra zoom afforded by point and shoots is often referred to as “empty magnification”. Much like digital zoom, empty magnification often results in a blurry picture, due to the fact that no new image information is gained despite the image being magnified.
Our list would not be complete without smartphone cameras, the most popular imaging device in the world.
By combining numerous cameras and image sensors, today’s smartphones are capable of achieving remarkably large magnifications. However, the use of multiple camera systems also makes smartphone cameras notoriously difficult to compare.
For example, consider a mobile phone that has a default “1X” lens with a 4mm focal length on a 1/2.3” format sensor.
Now, consider that that same phone has a “2X” lens with a 6.5mm focal length on a 1/3.5” format sensor.
You might expect the “2X” lens to have double the focal length of the “1X”, but smartphone companies often opt to use a smaller sensor due to depth constraints. Because this smaller sensor can only receive a portion of the light that this lens gathers, much of the potential magnification is lost—thus resulting in what is actually “fake” optical zoom.
DoubleTake: A Transformative Imaging Device For The Outdoors
So with all of this in mind, what makes DoubleTake so special?
DoubleTake™ has a binocular magnification of just over 10X, which is the equivalent of a 500mm focal length lens in a 35mm camera. Although this focal length number is a 35mm equivalent, DoubleTake™ achieves this focal length while maintaining an F-number of 1.8—an impressive feat, considering that most point and shoot cameras sport a 6+ F-number.
With these performance specifications, DoubleTake™ is capable of capturing ultra high-resolution pictures that can be zoomed in to the pixel level, all without losing a substantial amount of detail.
By combining this imaging power with disruptive form factor, we believe that DoubleTake™ becomes more than the sum of its parts—in essence, a truly next-generation imaging device that will change how people view the world around them.