Samsung provides a deep dive for the Galaxy S21 Ultra's new 108MP camera sensor
The Ultra was the only Galaxy S21 variant to debut with an 108MP sensor, leaving its siblings to make do with a top resolution of 64MP. Oddly, the highest-end model's new camera is not the ISOCELL HM2 that launched in late 2020, but is the HM3 instead.
This CMOS is 1/1.33 inches in diagonal length, as are some of its predecessors. However, it also makes the leap to 9:1 binning, which means each pixel forms a 3x3 single-color grid. This allows the HM3 to simulate 12MP images made of relatively massive 2.4 micron (μm) pixels.
Furthermore, considering each actual individual pixel is 0.8μm in size, that's a strong concentration of grids. Then again, Samsung insists that actual 108MP images (with the light for them) is still available through advanced resolution-switching IP.
Smartphone cameras might struggle when the light available to them changes gradually. Samsung claims to have solved this in the HM3 through Smart ISO Pro. This is a form of high dynamic range (HDR) imaging based on intra-scene dual conversion gain (iDCG).
The ISOCELL HM3 also features Super PD Plus, which consists of micro-lenses optimized for auto-focus (AF) tasks laid over the phase-detection (PD) focusing array. This is rated to increase its measurement accuracy by 50%, thus potentially benefitting low-light use and keeping focus on moving subjects.
Samsung has put the HM3 into mass production, so that Galaxy S21 Ultra units (and its possible immediate successors) might be kept in new top-end sensors. It will be interesting to see if it can improve on the underwhelmed reception the Xiaomi Mi 11 and its older 108MP camera has gotten thus far.