Back in 2016, the iPhone 7 Plus popularized “optical zoom” on smartphones. In recent years, it’s basically become a must-have on flagship smartphones. But why did I use quotes there?OK, quick nerd talk. Technically, most smartphones don’t have optical zoom. The term suggests that whenever you are moving that zoom dial, lenses would move and you would get physical optical magnification each step of the way. In the world of smartphones, we have multiple cameras, each with their own lens. The “regular camera” has a wide-angle lens, the secondary camera has a magnification lens. Any step between the two is digital zoom.
That said…
Is 5x zoom on the Galaxy Note 20 Ultra actually useful?
So, on to the latest and greatest. The Galaxy Note 20 Ultra has a 5x optical zoom lens. Sounds impressive at first, right? Yeah, but when I got to using the phone it dawned on me that I very rarely go up to 5x (focal length equivalent of 130 mm). That’s quite the magnification and you need to step way back if you want to snap your subject with the telephoto camera.
Even Samsung knows this. When you go into Live Focus mode (Samsung’s Portrait Mode), you only get 2x of digital zoom from the main camera for a portrait.
Now, OK, the main wide-angle camera has a high-resolution sensor and Samsung employs a lot of sharpening in post-production. So, is its digital zoom that bad? Is there actually any benefit to the optical zoom of this or any other smartphone camera module?
Well, let’s see…
Digital zoom vs optical zoom
I went out on a walk and took photos of a couple of scenes. In one photo, I had the zoom dialed up to 4.9 times, so the phone wouldn’t switch to the telephoto camera. In the next sample, I go up to 5x zoom and get the magnification lens. Is there any difference? Let’s check!
Scene 1: cathedral walls
4.9x digital zoom
5x optical zoom
The 4.9x zoom photo looks pretty OK, considering what it is. But then, as soon as you switch to the 5x photo, everything becomes better. Colors pop, details get sharp, reliefs and indentations in the bricks come to life. There’s a pretty obvious difference.
Scene 2: town clock
4.9x digital zoom
5x optical zoom
A high-dynamic scene, which required HDR to kick in. That, in turn, messed up the post-processing sharpening. The 4.9x photo definitely looks noticeably worse. And you can clearly see how aggressive the software sharpening is by the white halo sticking out of the clock arms.
Again, the telephoto proved it’s usefulness.
Scene 3: engravings
4.9x digital zoom
5x optical zoom
Again, the 4.9x zoom photo looks pretty OK, since I was standing quite some way back. You can definitely make out what that engraving is all about, right? But switch to the 5x telephoto picture and it’s like a night and day difference. We get the full details of the soldiers in the image and much better view of the marble bricks.
Another win for the telephoto!
Conclusion
Well, would you look at that… there is quite a difference! At 4.9x zoom, details do get smudgy. We can clearly see that there was some software sharpening going on, so the photo is not repulsive to look at. But fine details and shapes are much, much sharper when the phone switches to its secondary, 5x camera. Well, it was to be expected, but we had to check if it’s just marketing talk, right?
Unfortunately, some old rules still apply. If there isn’t enough light in a scene, the phone will prefer to use the main sensor with digital zoom. This is because the main sensor still has bigger pixels (with pixel binning) and will — presumably — perform better in low light conditions, compared to the sensor under the zoom camera.
That’s why we only tested this in daylight. Indoors, you have a 50/50 chance to get a digital crop when you go up to 5x. If you go to double-digit zoom, the phone is forced to go into hybrid focus, which means it switches to the telephoto lens, even if lighting is bad.
