Allow us to explain. The past year and a half has seen megapixel counts soar in most phone cameras. At the time of writing, we had smartphones with 108-megapixel sensors – indeed, Samsung’s own Galaxy S20 Ultra is one of them. Now, in almost all cases, the high megapixel sensor is the main sensor. It is the one that the camera is set to by default. For instance, the OnePlus 7T Pro has a 48-megapixel main sensor, or the Redmi Note 9 Pro Max has a 64-megapixel main sensor. Of course, it is not set to take images at 48 or 64 megapixels by default but gives you the option to take that large a picture and crop it to a smaller one, to focus on a certain part, without losing too much detail. Many of these devices have also come with dedicated telephoto sensors that allow you to zoom in without losing detail, just like you would on a proper camera. However, in most cases, the telephoto lenses have a lower megapixel count, which actually limits the amount of detail you can get. So for instance, on the OnePlus 7T Pro, the telephoto sensor is an 8-megapixel one, so your images are likely to be limited to a size of 8 megapixels. Which is kind of all right if you like about 2x or 3x zoom, but then starts pixelating very badly beyond that. Some manufacturers try to get in a bit more detail by having a hybrid zoom feature which also gets details from the main sensor, but this is an iffy process. Some brands have tried to make telephotos more effective by making the telephoto sensor almost as good as the main one (at least in megapixel terms) – the iPhone is a prime example, OnePlus did give the OnePlus 5 a 20-megapixel telephoto shooter (its main shooter was 16 megapixels), and Xiaomi also gave the Mi A1 a 12-megapixel telephoto sensor just like the main one – but by and large, the rule has been to give the megapixels to the main sensor. The rationale has varied from costs (two sensors of almost the same quality as the main sensor can hit budgets) to hardware issues (accommodating two large sensors in a camera unit). Indeed quite a few manufacturers have done away with the specialized telephoto sensor altogether, relying instead on the big megapixel main sensor to try and deliver some zoom goodness.
The Samsung Galaxy S20 series, however, has finally got the concept of the smartphone telephoto sensor spot on. All three of the phones in the series – the S20, the S20+, and the S20 Ultra come with massive telephoto sensors. The S20 and the S20+ have 64-megapixel telephoto sensors, while the S20 Ultra has a 48 megapixel one (in physical terms, however, it is the largest of the lot, being a half-inch sensor). Interestingly, both the S20 and S20+ have 12 megapixel main sensors, while the Ultra has an enormous 108-megapixel one. And this resulted in some of the best zoom shots we have taken with any camera phone. Check the samples – we did not even know there was a cat in the parking lot until we started zooming. Similarly, we could zoom into leaves on a tree, and of course, suddenly shooting the sun was on! Yes, there is a lot of software wizardry going on but in broad terms, the S20 series simply throws the kitchen sink at telephoto sensors as far as phone photography. Yes, the telephoto sensors do not take 48 megapixel or 64-megapixel shots to make the most of pixel binning, but you not only get the 2-3x optical zoom that you normally get in most telephoto sensors but thanks to their high megapixel count of the sensors, the digital zoom actually becomes much more effective. You can crop out far more of the image without losing too much detail. And this actually makes the telephoto lens a whole lot more effective. No, the execution was not perfect – we saw pixelation creeping in sometimes and sometimes got relatively clean shots but the theory was very sound. More zoom with more megapixels seems to work better than more zoom with fewer ones. We had actually noticed that with the OnePlus 5, whose telephoto sensor was one of the most underrated we have seen. Thanks to the physical limitations of smartphone design, a telephoto lens in a smartphone cannot stretch out from the camera as it does on a DSLR. So digital zoom becomes very important indeed, as it allows users to go beyond the usual 2x-3x of optical zoom. Yes, hybrid zoom can improve matters, but any way you look at it, having more megapixels on the telephoto sensor really helps. Samsung, we think, has got smartphone telephotos right, with the S20 series. The big question is: will others follow suit?
