ANAFI’s innovative imaging system technology enables you to zoom up to 2.8x without losses in 1080p and up to 1.4x in 4K. Learn all about ANAFI’s unique lossless digital zoom in this article.
What is a lossless digital zoom?
By definition, lossless zoom means that no loss in the quality of the image will occur when scaling it up.
Let’s start by explaining how a standard digital zoom works. The close-up effect is created artificially by scaling up the pixels of an image after it has been taken. The image is cropped down to a centered area with the same aspect ratio as the original. By doing this, each pixel is enlarged and therefore the quality is downgraded.
Lossless digital zoom works in exactly the same way. However, the difference comes from the number of native pixels shot: lossless digital zoom will capture many more pixels than the final definition of the picture.
In ANAFI, the 21MP sensor can capture the stills of a video with more pixels than required to record in 1080p or in 4K, so the image processor can crop these images to scale them up without degrading the quality.
Fig 1. ANAFI’s sensor size compared to 4K
The processor interpolates the pixels contained in the scaled-up output image. Using this oversampling technique, we can maintain the pixels of the displayed image at the same size as the sensor pixel one even after it has been cropped and resized.
Fig 2. Lossless zoom (x2): interpolation of pixels to keep them at the same size
What is the difference between an optical and a lossless digital zoom?
Optical and digital zooms are quite different. In the former, the enlargement is achieved mechanically by moving the glass elements inside the lens, in order to reach a higher focal length. All the magnification is done using the lenses, therefore the image projected by the sensor is scaled up by the optical lenses, without any loss in quality.
On the other hand, a digital zoom is achieved without any mechanical action inside the lens. Contrary to the heavy, cumbersome and fragile optical systems, a lossless digital zoom can be accomplished smoothly and very quickly, with no impact on the focus, allowing you to create amazing effects like Dolly Zoom. It is the ideal solution for a small, compact and lightweight drone, and offers the same quality as an optical zoom.
How do you estimate the maximum lossless zoom value?
Let’s do some math here !
The accurate estimation of the lossless zoom value takes into account the number of pixels of the image sensor, as well as the magnification and distortion of the lens.
With the camera design of ANAFI, the minimal zoom value (1x, which means no zoom) for 4K UHD corresponds to one pixel displayed on a 2-pixel area on the image sensor, as shown on figure 4. Let’s call TS the surface of a sensor pixel, and Ti the surface of the image pixel. We can then easily write equation (1).
Fig 4. Comparaison entre la taille d’un pixel du capteur et la taille d’un pixel image, pour une image 4K sans zoom.
As explained in this article, a lossless zoom means that the quality of the image remains constant even after the image has been zoomed in. The maximal lossless zoom factor is defined in the center of the image and corresponds to the configuration for which one pixel of the final image (displayed pixel) occupies the surface of one pixel of the image sensor (cf. figure 5).
Fig 5. Comparaison entre la taille d’un pixel du capteur et la taille d’un pixel image, pour une image 4K avec la valeur maximale de zoom sans perte.
Let’s call Z the zoom factor and Pi’ the surface of a pixel of the image after it has been zoomed in. We have then the following equation:
We’re searching the maximum value of Z to get a lossless zoom, which is reached when the size of the image pixel Pi’ equals the size of the sensor pixel Ps:
By combining the previous equations (1), (2) and (3), we can obtain the value of Z:
For the 1080p format (2.1 MP), an image contains 4 times less pixels than a 4K UHD image (8.3 MP). This means that one image pixel in 1080p occupies 4 times more surface than the 4K image pixel. Instead of having an image pixel size that covers 2 sensor pixels, one 1080p image pixel occupies 8 sensor pixels, in other words:
By developing the same calculations as earlier, we can find the maximum lossless zoom factor for 1080p, which is:
These calculations prove that lossless zoom is the perfect technology for your footage, always maintaining optimum quality no matter where you are.
How can I use this new feature?
The zoom offers plenty of new perspectives. You will be able to record crystal-clear shots of subjects in the distance without moving your drone.
It’s the perfect solution if you want to zoom in on an animal you see outdoors. In the following photos, we zoomed in on a lama with ANAFI. The quality of the second image is as clear as the first.
Zoom out and you can see the stunning backdrop in its entirety. In the photos below, ANAFI zoomed out on an eagle, revealing the mountain on which the exquisite bird was sitting on.
Let your creativity run wild, by producing videos like cinema professionals! The zoom can help achieve great shots with cinematic effects. Either automatically, with the Dolly Zoom effect, or manually if you’re an accomplished pilot. Once you master all the piloting commands, you will be able to fly the drone in all directions while zooming in or out using the ergonomic Parrot Skycontroller 3.
Last but not least, you can always use the zoom capabilities of ANAFI to save battery life. From the air, you can zoom in on various areas to check which are the most flight-worthy, instead of flying there and back.