Flashback: smartphone camera sensors grew not only bigger, but smarter too
When it comes to film photography, 35mm was by far the most popular option and was used on everything from simple point-and-shoot cameras to expensive SLRs. It was so common that lens focal lengths are still usually listed in 35mm equivalents. The digital transition brought the “full frame” DSLRs, where the size of sensors matched the size of a 35mm still. However, it also brought smaller digital cameras – small enough to keep in your pocket.
For them, the 1″ sensor is the holy grail, with cameras like the Sony RX100 series being a popular example. They fell out of fashion as smartphone cameras improved significantly in capability, but they had an impact on smartphones.
The Sony Xperia Pro-I borrowed the 1” sensor from its RX100 cousins, although it doesn’t have the optics to make full use of it (it’s a 20MP sensor, the Pro-I only uses 12MP of it). We should note that the so-called 1″ sensors don’t actually measure 1 inch in size, they’re more like 2/3″. Like the 35mm thing, this is another holdover from old cameras.
The Sony Xperia Pro-I borrowed a 1″ sensor from the RX100 series of premium point and shoot cameras
Anyway, the Pro-I image sensor has impressively large 2.4µm pixels – the 200MP ISOCELL HP3 we talked about last week only goes up to 2.24µm pixels with 16-in-1 binning. These two sensors are of course designed for two different cameras with two different uses.
You probably know that the Pro-I is not the first smartphone with a 1” sensor, and it certainly won’t be the last – 2023 promises to be the year when this type of sensor becomes the norm for flagships.
Some of you may remember the Panasonic Lumix Smart Camera CM1. The design of the case leaves little doubt that this is a camera phone, and it featured impressive brand-name hardware: a 20MP 1″ sensor behind an f/2.8 Leica lens and a “Venus engine” capable of recording 1080p videos at 30fps (and 4K at 15fps).
The Panasonic Lumix Smart Camera CM1 is an early example of a smartphone with a 1″ sensor
It was a thick phone with a thickness of 21mm and a weight of 204g (okay now, a lot for 2014). The CM1 ran Android 4.4 and the custom camera app offered full manual control.
A really cool feature was that the silver ring around the lens was actually a dial that can be used to change the settings of the camera. The Lumix CM1 cost a whopping $1,000, which at the time was considered expensive, but not too bad for such a specialized piece of kit.
Let’s go even further back in time. We’ve talked at length about the Nokia 808 PureView, a phone so advanced it felt like it was from the future. When it came out in 2012, no other phone could really challenge it and its absolutely massive 1/1.2” sensor. The Toshiba HES9 dwarfed the sensors of modern phones – here it is next to the paltry 1/3.2” Sony IMX145 (8MP) used in the Galaxy S III from the same year.
The massive 1/1.2″ sensor (Toshiba HES9) on the Nokia 808 PureView
The PureView sensor had quite large pixels even by modern standards, 1.4µm, and lots of them too – 41MP. As we discussed last week, the first smartphone to beat it in the resolution game didn’t come until 2018.
And it was precisely the high resolution that made the Nokia 808 feel so futuristic – the supersampling technology used was standard for 8MP images, producing stunning per-pixel quality and enabling lossless digital zoom. Modern smartphones use a very similar approach, albeit with some important differences.
By the way, if you’re wondering how the Nokia 808 PureView compares to a modern smartphone, last year we put it to the test.
We compared it to the Xiaomi Mi 11 Ultra, the phone with the biggest camera sensor of its time – the Samsung ISOCELL GN2 was bigger than even the 808’s sensor with a 1/1.12” optical format (at 50MP, giving 1.4µm pixels).
The Xiaomi Mi 11 Ultra packed a huge 1/1.12″ sensor that outperformed the 808 PureView (in more ways than one)
We’re going to take a little detour here and talk about pixels. When talking about digital cameras, you often see details about aperture, sensor and pixel sizes listed. But not all pixels are born equal.
The 808 PureView’s sensor may have been impressively large and very high resolution, but it was outdated technology. It was a Front-Side Illuminated (FSI) sensor, which means the sensor circuitry gets in the way of the photodiodes. The Lumia 1020, Nokia’s next 41MP phone launched the following year, used a smaller (1/1.5”) Back-Side Illumination (BSI) sensor.
Front lighting, aka FSI vs. Backlighting, aka BSI (image credit)
That’s not all either. The name “ISOCELL” comes from the physical barriers that isolate individual pixels, reducing cross talk. Samsung continued to develop the technology and touts many more advantages (eg greater well capacity, which measures how many photons a pixel can collect before hitting its maximum).
The transition from BSI to ISOCELL and the continued development of ISOCELL
Samsung is not alone in this design, OmniVision for example has a similar technology called PureCel Plus:
There are other new developments, like Sony’s stacked sensor design, which separates the photodiodes and transistors that read them into two separate layers instead of having them side by side, increasing the surface area of the photodiodes.
Sony is developing a stacked CMOS sensor design
All of this is to say that pixel size alone is not the ultimate measure of image quality. In fact, it’s clever designs like these that have allowed sensor manufacturers to shrink pixels to as little as 0.56 µm (fun fact: the 150MHz Pentium Pro from 1995 was manufactured on a 0.5 µm node and had 5.5 million transistors).
The successor to the Mi 11 Ultra is the Xiaomi 12S Ultra, which switched teams and has a Sony IMX989 sensor for its main camera – an impressive 1” 50MP sensor. That’s much larger than the 1/1.5″ commonly found in phones today and even 1/1.3″ sensors. The Pixel 7 and iPhone 14 Pro fall into this category and have comparable resolution (and thus pixel size). The Galaxy S22 Ultra also has a 1/1.3” sensor (a hair smaller), but due to its 108 MP resolution, its physical pixels are smaller.
The current state of the art for huge smartphone sensors: 1″ Sony IMX989 used in Xiaomi 12S Ultra
But before the 12S Ultra, there was another phone to use IMX989 – the Sharp Aquos R6. Funnily enough, the Aquos was also emblazoned with the Leica logo, which co-developed the camera with Sharp. So it has it in common with Xiaomi. Sharp is responsible for many firsts in the mobile industry, although the brand’s limited presence in the smartphone market means that these ground-breaking phones often fly under the radar.
Sharp Aquos R6 was the first with IMX989 and its camera was also co-developed with Leica
Rumors are circulating that several smartphone manufacturers are working on flagships with 1” sensors, specifically one with medium resolution and large pixels. There will also be some models with 200MP cameras and smaller pixels. We can’t wait to see how the battle between the two philosophies will develop.