How do some mobile phones camera manage to get ISO 409600?

[hap2001]

Hello.
I just saw some Chinese cellphones that have camera with ISO 102400 or even 409600, which is the same as the famous Sony A7S series... How is that possible?
Seems it's doing both pixel binning and multi frame stacking? So it cannot record video at that ISO?
What's the "real" ISO of that phone camera?
And what do you think the theoretical ISO limit for such a small sensor like 1/1.7-1/2.5?
Thanks.

[tooki]

I assume they achieve it the same way they achieve 20000mAh 18650 lithium ion batteries: by lying.

Ok, it’s not exactly the same: you can boost the gain on a tiny sensor the same as on a big one. But the noise will be much, much worse. So the resulting images will either be way noisier than the already super noisy images from the A7S at that ISO, and/or they’ll apply even more severe noise reduction, which will render them with even more watercolor effect than the already very water effect riddled images of the A7S at that ISO.

Yes, it’s possible for different noise reduction algorithms to produce better results than others, but miracles are not possible.



Digital sensors do not have a “native” ISO. The ISO is basically a gain setting for the readout amplifiers. Nor is there a real or theoretical limit to ISO as such; it’s just the tradeoff of signal to noise. Eventually your signal disappears into the noise. Before that happens, you choose a balance of sensitivity to noisiness.

[voltsandjolts]

Don't know what ISO it achieves, but my phone is incredible at taking photos in low light. It must be stacking multiple images, shifting each of them to line them up as the camera moves a bit, getting an exposure of several seconds without the motion blur.