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What you need to know about Samsung's new ISOCELL sensors
At this year’s second MWC, this time in Shanghai, Samsung announced a new brand of ISOCELL image sensors, which are almost certainly heading to future smartphones under the company’s Galaxy brand and possibly beyond. The new range consists of the ISOCELL Bright, Fast, Slim, and Dual, the latter of which certainly hints at a dual camera option for upcoming Galaxy Note 8. So let’s take a closer look at what Samsung’s technology has to offer.
What is ISOCELL?
ISOCELL is Samsung’s brand name for its range of CMOS image sensors that are built using an unconventional sensor design layout, when compared to the more common back- and front-side illuminated sensors produced by other manufacturers. This design is based on 3D-Backside Illuminated Pixel technology with Front-Side Deep-Trench Isolation (F-DTI) and Vertical Transfer Gate (VTG), which boasts a number of improvements in terms of light capture. Despite the banding launch, Samsung’s ISOCELL has actually been around since 2013 and made its debut inside its Galaxy S5 flagship.
Put briefly, the technology was built to help reduce the crosstalk issue that occurs inside small pixel sized camera sensors. In smartphones, camera pixels are incredibly small and packed closely together, resulting in some inevitable light bleed between the RGB cells which produces additional noise called crosstalk. By better isolating these photodiode cells (hence the name ISOCELL), Samsung is able to increase the sensitivity of these camera pixels, resulting in better light capture and lower noise despite the compact sensor size.
Closer look at the latest sensors
For the most recent announcement, Samsung has optimized its ISOCELL technology down into four different packages designed for more specific use cases and target markets. Here’s how they each break down in terms of features and likely implementations.
We’ve seen a number of smartphone manufacturers make the move over to dual camera setups over the past few years, and it’s a trend that Samsung now appears confident enough to join. ISOCELL Dual is Samsung’s implementation of the monochrome + RGB sensor configuration that we’ve seen used quite successfully by Huawei in its dual camera smartphones. A similar technology is also promoted by Qualcomm under its Clear Sight brand.
As with previous implementations, the idea is to marry higher dynamic range monochrome sensor data with traditional RGB data to give a picture an improved HDR look. This design also has the added benefit of reducing noise in low light situations, something that all single sensor smartphone cameras struggle with to some extent.
In terms of specifications, Samsung’s dual camera configuration offers up two 13-megapixel sensors, one RGB and one black and white, both with Samsung’s autofocus technology on board. Both cameras feature smaller 1.12 µm pixel sizes than Samsung’s current high end 1.4 µm sensor inside the Galaxy S8, a necessary trade-off given that Samsung is doubling the number of sensors and therefore pixels. There’s also an f/2.0 aperture on board, which lets in less light than before. However, Samsung says that these sensors can be mixed and matched in various combinations, so we may see different variants too.
ISOCELL Dual marries higher dynamic range monochrome sensor data with traditional RGB colors for superior HDR, less noise, and better low light performance.
While it at first appears that light sensitivity may be worse than before in this setup, we must remember that the monochrome sensor will benefit from less crosstalk, greatly improving its overall sensitivity to light and dark. Combining this data with color data from the RGB sensor should, in theory, actually result in less noise and greater dynamic range than a single sensor setup.
Based on the fact that the example sensors boast the same resolution and aren’t using a “telephoto” lens, it’s seems unlikely that ISOCELL Dual will be touting optical zoom capabilities. That’s because the camera focal lengths are the same, and there isn’t any resolution cropping that can be applied to produce a digital/optical hybrid zoom effect in the same vein of Huawei or OnePlus. This could change based on how Samsung implements its technology in an actual smartphone, however.
Samsung says that its lineup of Bright sensors are designed to “deliver bright and sharp images with high color fidelity and reduced noise in low light environments”. That doesn’t reveal very much about the range, and given that this is basically what ISOCELL was designed to do this might just end up being the name that Samsung uses for the majority of its sensors going forward.
The company hasn’t revealed the specifications of its Bright sensors just yet, but I imagine that it will follow Samsung’s latest theme of using slightly larger sensor pixel sizes for superior light capture. Somewhere around 1.4 µm seems to be the sweet spot in smartphones right now, which is larger than the 1.12 µm that you’ll find in many of Sony’s sensors, for example. It’s doubtful that Samsung is planning to go quite as far as HTC’s 2 µm experiment with the One M8, as even the company’s latest Ultrapixel 3 camera uses the 1.4 µm convention.
“Samsung ISOCELL is a brand that represents the essence of our leading pixel technologies. We expect the ISOCELL brand to help consumers easily acknowledge and confide in camera performance as well as overall quality of the device,” - Ben Hur, Vice President of System LSI marketing, Samsung Electronics
Again, I suspect that the Fast moniker is another rebranding exercise for another of Samsung’s existing camera technologies. The company debuted its impressive Dual Pixel phase detection autofocusing (PDAF) technology inside last year’s Galaxy S7 flagship and continues to integrate this technology into its high-end camera modules. Unlike old contrast image analysis, PDAF uses the phase of light hitting the sensor’s pixels at different points in order to determine an object’s distance, but this requires additional hardware baked into the sensor’s pixels.
Rather than using only a few pixels for traditional phase detection autofocus, Dual Pixel technology uses every pixel in the camera sensor to assist with focusing. The end result is much faster focusing and a greater ability to maintain focus on fast moving objects. Samsung isn’t alone in using Dual Pixel autofocusing any more though, a number of high-end sensors for other vendors can achieve similar results.
Essentially, ISOCELL Fast sensors will be models that incorporate this technology, while presumably the regular Bright variants will use more traditional PDAF and will be a little less expensive.
Samsung’s Slim model is a slightly different take on the ISOCELL formula, using the enhanced design to actually slim down the side of the camera module for low profile designs. Samsung clearly heard that consumers don’t like camera bumps, but this is usually a necessary trade off in order to use larger, higher quality sensors inside a slim phone.
By making use of ISOCELL’s superior photodiode isolation characteristics, Samsung is able to shrink its sensor pixel sizes down to just 0.9 or 1.0 µm. Essentially, this sounds like a revision of the company’s BRITECELL technology that it announced back at the end of 2015.
This wouldn’t be very feasible with traditional BSI designs because the amount of noise ramps up significantly as pixel sizes shrink. With ISOCELL Slim, Samsung should be able to offer high resolution, compact image sensors without sacrificing too much in the way as image quality. Though, these sensors won’t produce the same quality results as the Bright or Fast variants.
ISOCELL technology isn’t a new venture for Samsung and this latest announcement looks mostly like a rebranding exercise in order to fit all of its existing camera technologies under a single brand name. This isn’t a bad move though, as consumers and Samsung’s CMOS customers will be able to more easily tell what features they’re buying in the future.
The only major innovation announced is the introduction of dual camera modules using Samsung’s ISOCELL technology, which will combine Samsung’s existing hardware leadership with new software techniques for better looking pictures. This is a very promising prospect for smartphone photography, particular for low light shots, and one that we’ll undoubtedly see used in handsets soon enough.