Are Sony, Huawei, and Samsung Going Too Far With 48MP Sensors for Phones?

Are Sony, Huawei, and Samsung Going Too Far With 48MP Sensors for Phones?

Honor and Xiaomi have both pre-announced phones using new 48MP sensor designs. Huawei subsidiary Honor’s View 20 — officially launched this week — taps Sony’s IMX586 version, and Xiaomi is teasing a 48MP model with an unknown sensor, perhaps either Sony’s or Samsung’s similar chip. Whether phone makers use Sony or Samsung for the new models, base specs are fairly similar. Both companies sensors are a bit larger than most current phone cameras, at 1/2.0 inches. That still gives them tiny .8 micron pixels, but they each offer 4-photosite binning to natively output 10MP images. Like previous super-high-resolution sensors for phones, this raises the question of whether they’ve passed the point of diminishing returns on resolution, and have indeed gone so far in that direction that they’re just adding processing overhead without increasing image quality.

Since neither of these phones or any others with the new 48MP designs are available to test, we’re stuck with speculation. However, the Huawei Mate 20 Pro is available and features an oversized 40MP sensor with binning. I set out to see just how much it helps to have all that resolution at your disposal. I shot the same indoor test scene with the Mate 20 Pro in 40MP mode and 10MP mode, as well as with a Google Pixel 3, using features of the best “traditional” smartphone camera designs.

Google’s HDR+ Is Almost Like Having a Higher-Resolution Sensor

I started my testing by capturing JPEGs at each phone’s default settings. As expected, I could zoom in further on the images from the 40MP Mate 20 Pro, But what I wasn’t entirely prepared for was that it didn’t appear to do a noticeably better job of resolving detail (in either the 40MP or 10MP mode) than the Google Pixel 3. From looking at the EXIF data I realized the secret was Google’s HDR+. The Huawei bumped the ISO up to 500 to get a 1/50s exposure, while the Pixel 3 took some number of frames at ISO 79 and 1/24s. Since I had the phones on a tripod with a timer, the situation was ideal for the computational imaging of the Pixel 3 to align and combine the images.

A Huawei Mate 20 Pro 40MP test image. To get a sense of the detail captured, click on the image, and then zoom in to the text on the SpyderCheckr chart, for example.
A Huawei Mate 20 Pro 40MP test image. To get a sense of the detail captured, click on the image, and then zoom in to the text on the SpyderCheckr chart, for example.
A Google Pixel 3 12MP test image. Clicking on and zooming in on this image shows approximately the same amount of detail as with the 40MP image, thanks to Google’s HDR+ multi-frame processing.
A Google Pixel 3 12MP test image. Clicking on and zooming in on this image shows approximately the same amount of detail as with the 40MP image, thanks to Google’s HDR+ multi-frame processing.

So that was lesson one. That, given the right circumstances, clever software can emulate the performance of higher-spec hardware. But I was still curious about the sensors themselves. To compare those, I realized I’d need to shoot RAW rather than JPEG. Both phones allow you to record RAW (DNG) images, although there is no standard for the type of pre-processing that might have snuck into what either calls a RAW image and to look at the image I needed to open them in Lightroom. So this isn’t a perfect test of the sensors, but with all Lightrooms adjustments turned off, it is about as close as possible:

A zoomed-in, actual-pixels region from a RAW image captured with the 12MP camera on the Google Pixel 3.
A zoomed-in, actual-pixels region from a RAW image captured with the 12MP camera on the Google Pixel 3.
A zoomed-in, actual pixels region from a RAW image captured with the 40MP camera on the Huawei Mate 20 Pro. This is a smaller area of the entire image, of course, since it is actual pixels and the image has higher resolution.
A zoomed-in, actual pixels region from a RAW image captured with the 40MP camera on the Huawei Mate 20 Pro. This is a smaller area of the entire image, of course, since it is actual pixels and the image has higher resolution.

The good news for fans of high-resolution sensors is that you can indeed make out more detail in the 40MP RAW than in the 10MP RAW. On the flip side, you can also see that if you’re simply looking at your images on a phone screen — like 95 percent of the planet — you won’t notice any difference. I wanted to do the same experiment using the 10MP binned output from the Mate 20 Pro, but it can’t output RAW data at that resolution.

More Cameras Might Be Better Than More Resolution

As interesting as the 40MP main sensor on the Mate 20 Pro is, I’ve found its use of 3 cameras much more exciting. In addition to the main sensor, it has an 8MP 3x telephoto camera and a dedicated 20MP wide-angle (16mm equivalent) camera. While a number of other phones have a telephoto lens, most are only 2x, which doesn’t help too much when shooting distant subjects. The third, wide-angle, camera is only found in a very few phone models, like the LG V40, but the one in the Mate 20 Pro is even wider. Combined with the other two lenses, this was the first phone that made me feel like I was using a true Interchangeable Lens (ILC) camera. I realize it isn’t a simple tradeoff, but personally, I’d encourage phone makers to look at the creative use of multiple cameras before they invest too much in trying to cram super-high-resolution sensors into them. Several phones are in the pipeline using arrays from Light.co, for example. It’ll be interesting to see how far they can put the envelope for phone imaging.

In many cases, you can use the Panorama mode of your camera to capture a larger composition, but it takes time and doesn’t work well if anything is moving. That’s where having a dedicated wide-angle camera comes in handy. To give you a sense of how much more of the scene the wide-angle lens captures, here is the wide-angle image of the same scene captured with the Mate 20 Pro:

A wide-angle — 16mm equivalent — of the same scene captured with a Huawei Mate 20 Pro.
A wide-angle — 16mm equivalent — of the same scene captured with a Huawei Mate 20 Pro.

What to Do When Your Next Phone Has a 48MP Camera

I can already tell it’s going to make for plenty of sparks flying when more high-resolution phone cameras are introduced, as in some situations they’re likely to provide jaw-dropping results, and in others will simply clutter up more of your phone’s precious storage space. As a practical matter, I think most shooters will be best served by leaving their phone’s camera in the “binned” mode (10MP-12MP typically), which will save processing power and storage with little to no effect on most image viewing. But if you think you’ll need to do a lot of cropping on an image, or want the best possible starting point for a decent-sized print, then the native resolution makes sense. Of course, if you’re hooked on a RAW image workflow, that’ll be your starting point in any case.

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