Over the last couple of years, high megapixel sensors in smartphone cameras have become the norm. Huawei led the way with 40MP sensors. Then Sony launched the 48MP IMX586 Quad Bayer sensor in 2018. The sensor ended up being used by a huge variety of popular mid-range, flagship, and budget smartphones in 2019. The relentless march forward continued with the announcements of the first 64MP sensors in the form of the ISOCELL GW1 and the Sony IMX686 respectively. However, Samsung wasn’t content with that. The company broke new ground when it announced the 108MP ISOCELL Bright HMX last year, which ended up making its way to the Xiaomi Mi Note 10. The slightly upgraded ISOCELL HM1 featured in the company’s halo flagship, the Galaxy S20 Ultra. In the smartphone camera industry, primary camera sensors are now sourced from Sony or Samsung, and they have become the two dominant players in the market. Now, Samsung has announced another high megapixel sensor for smartphones in the form of the 50MP ISOCELL GN1. Interestingly, it has Dual Pixel autofocus. Let’s delve into the background of this news announcement.
While it may seem that high megapixel sensors are a win-win situation due to pixel binning, it’s not so simple as that. For one thing, a 48MP or 64MP or 108MP sensor doesn’t have 48MP/64MP/108MP of chromatic resolution. The Quad Bayer and Nona Bayer (Galaxy S20 Ultra) filter of such sensors means that in reality, a 48MP Quad Bayer sensor has only 12MP chromatic resolution. These sensors can produce high-resolution Quad Bayer output, but the results are usually less than optimal as they are not meant to be used that way. Instead, device makers still continue to ship their phones with pixel binned 12MP/16MP/27MP modes by default. The other major issue with these sensors is that up until now, these high megapixel sensors haven’t supported Dual Pixel PDAF. With the exception of the LG V60 ThinQ, all phones with such high megapixel sensors have relied on traditional phase detection autofocus (PDAF).
Dual Pixel PDAF, an autofocus technology that is popularly used in DSLRs and mirrorless cameras was first introduced in smartphone cameras with the Samsung Galaxy S7. It means that the image sensor uses 100% of pixels in the sensor for autofocus, significantly improving the speed and accuracy of the focusing system. The Galaxy S20 Ultra, with its 108MP high-resolution sensor, is actually the first Samsung flagship to lack the Dual Pixel PDAF system since the Galaxy S7, and it shows. At launch, reviewers pointed out various autofocus issues with speed and accuracy on the Galaxy S20 Ultra (review), which hampered the user experience. Samsung subsequently rolled out an update to fix such issues, but feedback still remains fixed on whether they have been completely fixed. Moreover, because of the hardware characteristics of PDAF vs. Dual Pixel PDAF, the S20 Ultra’s 108MP sensor will never be able to focus as fast or as accurately as the traditional 12MP primary sensor of the standard Galaxy S20 and the Galaxy S20+ (review). It’s clear that high megapixel sensors need to incorporate Dual Pixel autofocus to prevent any such issues in future phones, and the 50MP ISOCELL GN1 does just that.
Samsung 50MP ISOCELL GN1 image sensor
The 50MP ISOCELL GN1 is a large 1/1.3″ sensor with comparatively big 1.2μm pixels. The size of the sensor is actually slightly bigger than the 108MP ISOCELL HM1 used in the Galaxy S20 Ultra, which has an optical format of 1/1.33″. Samsung notes that the GN1 is the company’s first image sensor to offer both Dual Pixel and Tetracell technologies. The bigger pixel size is said to bring image sensor performance to a “new level” with a combination of elevated light sensitivity for better low-light photos and DSLR-level autofocus speeds. The Dual Pixel technology creates 100-million phase-detecting photodiodes for fast auto-focusing and light information that can be translated up to 100 megapixels, according to the company.
A balance needs to be made between detailed high-resolution photos and bigger pixels for better photos in low light situations. The ISOCELL GN1 strikes a relatively pragmatic balance between the two, just like the Sony IMX689 found in the OPPO Find X2 Pro (first impressions) and the OnePlus 8 Pro (review). According to Samsung, it thus fulfills multiple needs at once.
The GN1 has 100 million PDAF agents. Samsung’s Dual Pixel technology places two photodiodes side-by-side within a single pixel that can receive light from different angles for phase detection. With all of the sensor’s active pixels working as autofocus agents, the GN1 can detect and focus onto an object from every corner instantly, even in low light. During still image capture, a single-pixel output is created by merging the outputs from the two photodiodes within the pixel. The company also provides a software algorithm that takes light information from each photodiode to produce image resolutions comparable to 100MP (this seems to be an example of super-resolution).
The ISOCELL GN1 naturally also features Samsung’s Tetracell technology, which is nothing but the company’s name for 4-in-1 pixel binning (the Galaxy S20 Ultra, on the other hand, uses 9-in-1 pixel binning, i.e, nona binning). Samsung describes it as a pixel merging technique that improves the pixels’ capacity to capture and process more light. It doubles the “effective pixel size” to 2.4μm and quadruples the light sensitivity to take bright 12.5MP photos. The improved light sensitivity is because of the 1.2μm pixel size, which is higher than the standard 0.8μm pixel size of other high-resolution image sensors. The IMX689, on the other hand, features a slightly smaller 1.12μm pixel size, while the OmniVision OV48C has the same 1.2μm pixel size, but it hasn’t made its way to any phone camera yet. Even in extremely low light, the GN1 can supposedly deliver bright and sharp results.
The sensor also comes with Smart-ISO to intelligently select the optimal ISO. In addition, it features real-time HDR enabling it to capture the scene in multiple simultaneous exposures, as well as gyro-based EIS to take sharp photos and videos in motion. The GN1 supports video recording at up to 8K resolution at 30fps. Notably, this is higher than the capabilities of the Galaxy S20 Ultra’s 108MP sensor, which supports 8K at only 24fps.
Samsung says that the ISOCELL GN1 started mass production this month. However, according to notable leaker Ice Universe, this sensor won’t be making its way to the upcoming Galaxy Note 20+. The Galaxy Note 20+ will instead feature the same 108MP HM1 sensor that is found in the Galaxy S20 Ultra, but it will add a new sensor to completely solve the focusing problem. This should, in theory, prevent autofocus woes. The 50MP sensor won’t be making its way to the Galaxy Fold 2 either. It can be expected to find its way in a premium Samsung phone eventually, though.