Anyone who followed digital cameras around 10 or 15 years ago probably remembers seeing Exmor R CMOS printed everywhere.
Sony cameras had it. Smartphones started using it. Marketing materials loved talking about it.
And for good reason.
Exmor R introduced Sony's back illuminated sensor design, where the light receiving part of the sensor was positioned differently so less light was blocked by the wiring. The result was better sensitivity, particularly useful when taking photos in darker conditions.
At the time, that was a pretty big deal.
But camera sensors didn't stop there.
Sony later introduced Exmor RS, taking the back illuminated idea and adding a stacked design. Instead of squeezing the pixels and processing circuitry together in the traditional way, different parts of the sensor could be placed on separate layers.
Sony actually commercialised its first stacked Exmor RS sensor back in 2012. Sony's own history of the technology shows how this became an important part of its image sensor development.
So why does stacking matter?
Mostly because modern cameras need to do much more than simply capture a photo.
They need fast autofocus, 4K and 8K video, high frame rates, HDR, subject recognition, electronic shutters and increasingly sophisticated computational photography.
That means the speed at which information can be pulled from the sensor matters a lot.
This is why two cameras with similar megapixel numbers can behave completely differently.
A 50MP sensor isn't automatically the same as another 50MP sensor.
One might read the image much faster, produce less rolling shutter, handle highlights better or capture high speed video that another sensor simply can't manage.
And Sony is already pushing the idea further.
Its newer 2 Layer Transistor Pixel technology separates the photodiodes and pixel transistors onto different layers. Sony says this can increase the amount of signal each pixel can hold, improve dynamic range and reduce noise, especially in darker scenes. Sony Semiconductor explains the technology here.
This is where camera marketing becomes a little funny.
Consumers are still being shown numbers like 50MP, 100MP or 200MP because megapixels are easy to understand.
Bigger number. Must be better.
Except the really interesting improvements are increasingly happening somewhere most people will never see.
Behind the megapixel number.
Inside the sensor.
Exmor R helped cameras capture light better. Stacked sensors helped them process that light much faster. Newer designs are trying to squeeze even more dynamic range and image quality from individual pixels.
So perhaps the next time a new camera or smartphone launches, the megapixel count shouldn't be the first specification to check.
The sensor architecture might tell a much more interesting story.