One of the highlight features in Samsung's latest flagship smartphone, the Galaxy S21 Ultra, is understandably its 108MP primary image sensor. Alongside differences in display and form factor, the 108MP image sensor is a key differentiator between the S21 Ultra and the regular Galaxy S21.

The image sensor used for the S21 Ultra's 108MP main camera is a Samsung ISOCELL HM3 sensor. Samsung released a video this week outlining the image sensor and what makes it unique. While the video is, at least partly, marketing material, it nonetheless sparks interesting conversations about the impressive photographic technology in Samsung's smartphones.

As outlined in Samsung's video, 'each individual pixel is isolated with ISOCELL 2.0 technology to enhance light sensitivity and color fidelity.' The image sensor includes 'Nonapixel' technology, which Samsung claims 'boost[s] performance in low-light conditions.' When shooting in a dim environment, the image sensor automatically combines nine pixels into one big pixel to produce lower noise images in low-light situations.

Samsung's 'Nonapixel' technology allows the image sensor to combine pixels into larger pixel arrays of a single color in order to improve performance in low light. Image credit: Samsung

A re-mosaicing algorithm rearranges all 108M pixels in bright conditions to make use of the high resolution. The sensor’s Smart-ISO technology allows it to seamlessly switch between low ISO and high ISO shooting modes, which Samsung claims maximizes detail in bright conditions and low noise when shooting in low-light situations. Smart-ISO Pro combines sensor readouts from low and high ISO shooting modes to produce a single image with 12-bit color depth and an expanded dynamic range when shooting in mixed lighting. A staggered HDR mode uses a rolling shutter to combine images shot with different shutter speeds.

Samsung's ISOCELL HM3 image sensor has many fascinating photographic features. You can see the main features in this graphic, courtesy of Samsung. Click to enlarge.

These advanced technologies don't amount to much if the camera cannot accurately focus, so Samsung added its new Super PD Plus AF technology. Samsung says newly-designed microlenses on the phase-detection focusing pixels improve autofocus speed and accuracy, even in low light.

It's not Samsung's first outlining the technology in its latest ISOCELL image sensor. The Korean company released a couple of tech videos earlier this year, including one that discusses ISOCELL 2.0 technology and another that outlines Smart-ISO Pro. Both videos can be seen below.

A smartphone's photographic capabilities and performance go beyond megapixel counts and high-tech image sensors. Real-world use matters too. In February, we covered a photographer's video comparing the S21 Ultra to a Canon 1DX II DSLR camera.

To learn more about the Samsung Galaxy S21 Ultra, refer to our launch coverage.