Smartphone camera test: why you need a telephoto zoom
Photo and video quality is one of the biggest battlegrounds of modern phones. The rear camera array of many flagship devices is filled with three or four lenses and at least one of them is guaranteed to be a telephoto lens if you buy a modern flagship.
The question I see popping up more often these days is, “What good is a telephoto lens on a phone?” Sure, it ticks a box on a list of specs, and maybe 3x or 10x zoom sounds cool for marketing purposes, but does it serve practical purposes for most users?
Adding even more confusion to this discussion is another arms race in modern phones: the race for megapixels. Flagships like the OnePlus 9 Pro and Samsung Galaxy S21 Ultra feature a primary 48MP and absurd 108MP sensor respectively. With all those megapixels, there’s plenty of resolution to zoom in after taking the shot and get a range similar to what you’d get from a telephoto lens. Isn’t that as good?
With these questions in mind, I grabbed my Galaxy S21 Ultra and OnePlus 9 Pro and took a few shots with the super high-res main cameras and the telephoto lenses, then compared the two. I was surprised by what I found.
Why do you need a telephoto lens?
Before I get to my test results, I want to briefly explain how the telephoto lens is useful in general. The industry tends to favor ultra-wide lenses; the Pixel 5 The best example of this is with Google’s move to a wide-angle and ultra-wide setup from the Pixel 4 XL’s wide-angle and telephoto lens. Google’s rationale for the change was exactly what I’ll be looking at in my tests: that you can digitally zoom with the main camera to replace a telephoto lens. Ultra-wide-angle lenses are also incredibly useful, but it turns out telephoto has its place too.
Beyond the basic notion that having more options and flexibility is better in photography, there are many specific use cases for a telephoto lens. Wildlife is perhaps the classic answer, taking photos of animals without disturbing them or putting yourself in danger with potentially aggressive animals. On a similar note (with that first concern anyway) getting pictures of your kids without interrupting their play or drawing attention to the fact that you’re taking their picture. Using a telephoto lens in these situations can yield some of the best candid shots.
Action shots, whether it’s your child running or snapping shots of a football game, are often best captured with a telephoto lens from a distance. You can actually follow and capture the action better while focusing on a specific subject. On that last point, finding a subject you may not have seen is another benefit of a telephoto lens. Sometimes you miss a specific element while trying to take an entire scene. A telephoto lens will also give you different framing options as you might have the ability to crop something that was ruining your shot.
Hope this gives you a general idea of how and why you might find telephoto photography valuable on your phone, now let’s take a look at whether a dedicated telephoto lens is worth it. Due to a resolution limit on the tool we use for the image comparison slider, I had to reduce the resolution of the shots from the dedicated telephoto sensors, but my comparisons are based on the images in full resolution that are twice that of the samples in the slider.
Do it for the show
One of the most interesting things I encountered during testing was the impact of using the telephoto lens versus the standard lens on exposure. The phone makes decisions based on the entire scene it captures. If you’re doing a minor crop it won’t matter, but if you’re trying to simulate a 3.3x or 10x zoom it can have a big impact on the result.
Here is an example of a photo of a quilt on my porch taken with the full 108MP main camera on the Galaxy S21 Ultra and then with the 10x zoom. I used the same focal point for both. As you can see, the main camera shot is completely blown out compared to the zoom shot and loses a considerable amount of detail.
Here is a similar example of a garden gnome that is a little less healthy after winter. Again, I found exposure to sabotage the shot with the 108MP primary as it pushed the hat to a much lighter color. I also lost detail despite this cropping offering higher resolution than zooming.
You can clean up some of that with a little editing in your phone’s gallery, but that’s extra work. And you still won’t get as good of a result as I got with the telephoto lens in terms of capturing the photo as expected. This issue is most apparent when shooting at relatively short distances; in both cases, I was about eight to ten feet from the subject. As you’ll see in my next examples, this becomes less relevant as you shoot longer shots, although it has other issues.
Zooming isn’t everything
To test one of my stated use cases, I went to a nearby pond and took photos of wildlife, specifically herons. It was a mostly clear day so there was full sun and I was about 30-35 feet from the herons. Here, exposure was less of an issue as the zoomed subject and the entire scene were exposed equally, but I still prefer telephoto exposure.
One of the issues I encountered was getting the focus right for shooting from the 108MP and 48MP prime lenses of the Galaxy S21 Ultra and OnePlus 9 Pro, respectively. It’s less distracting on the OnePlus 9 Pro because the 3.3x zoom, at that distance, doesn’t alter the scene as deeply, but it was still harder to target the herons.
Switching to the Galaxy S21 Ultra, it was impossible to get a shot from the main lens that focused on the herons as well as the 10x telephoto. The birds are barely visible in the wide-angle shot and there are way too many other elements trying to grab the focus.
It’s all in the details
For my last test, I took the focus problem out of the equation by visiting a mural at a local pizzeria, assuming focus on the side of a building about 30 feet away wouldn’t wouldn’t be a problem for both lenses. I was right about that, but again I was surprised by the results.
Here is the photo of the OnePlus 9 Pro. I prefer the color result of the main lens in this case, but there is more grain in this image, which I didn’t expect.
With the Galaxy S21 Ultra, the colors are closer, but the grain is even more pronounced than with the OnePlus 9 Pro; the 10x optical zoom is by far the sharpest shot.
Why haven’t you tested an iPhone?
In case you were wondering why I excluded Apple from this little test, the iPhone 12 Pro and iPhone 12 Pro Max have a telephoto lens, but the big difference is that the iPhone only uses sensors 12MP. So, unlike those Android phones that pack a massive main sensor and 8-12MP telephoto lens, the iPhone retains the same resolution.
The main one is still, by far, the best lens of the iPhone 12 Pro models with its F/1.6 aperture, but the resolution drop is going to be significant to the point where comparing a primary digital zoom to the telephoto optical zoom is no longer relevant.
At the end of the line
There’s plenty of room to wonder if telephoto photography, in general, is necessary on a phone. I’m very supportive of it because I both love taking pictures of wildlife and have kids who often run at high speeds or play sports. There are photos and videos I’ve taken of them with my phones telephoto lens that I just wouldn’t have captured with a standard lens. However, for others, a telephoto lens may be less relevant.
That said, I honestly wasn’t sure how the telephoto lens would fare against the huge megapixel primary sensors and was surprised at how much better the results are with the true telephoto lens, especially in the case of the 10x zoom of the Galaxy S21 Ultra. And while that wasn’t part of my testing, another factor to consider is video quality; the digitally zoomed video from the main lens doesn’t compare remotely to the video output from the 10x zoom if you’re trying to capture something in the distance.
If you think one of the use cases for a telephoto lens fits your usage, don’t feel like you’re wasting money on a high-end flagship to get that bigger optical zoom. ; you’ll be grateful when you get that irreplaceable shot.