Smartphone low-light image quality factors
Camera questions from my good friend Jesse:
Hola Mr. Hodges!
I have a newish Android phone, Moto X Pure (following my trend of getting 6 month olf technology for half price), which has a decent camera (Sony IMX 230 1/2.4-inch 21MP BSI CMOS sensor and a dual-LED flash. F2.0 aperture and 4K video). It works well, but it pales in comparison to some phone’s ability in low-light situations.
Is that on the camera hardware, or the app?
Same with image stabilization – is that in the camera hardware, or the app?
I was pondering this while on hold and digging around the web, and thought you might have 2 cents to throw my way. Is there a camera app that is worth buying, or are the limitations mostly hardware?
Congratulations on the Moto X Pure, that is a very nice phone indeed! Moto is one of my fav phone companies and the fact they keep a basically stock Android on their Pure phone is just icing on the cake.
As for your question, I would say it is primarily hardware related as 21MP is a very high MP count for such a small sensor. Please see this sensor size comparison chart. You can see that the larger mirrorless/DSLR type sensors have exponentially more surface area (or light gathering area) yet they may have almost exactly the same MP as the sensor in your phone.
For example, I have recently been using a Nikon D750 and Sony RX1 which are both 35mm “full frame” sensors and they are approx 24MP. They are capable of exemplary low light performance by increasing ISO (sensitity) to 3200, 6400 and beyond with minimal noise. Sometimes faster lenses (i.e. lenses that let in more light) can also play a factor. However, your Moto has a fairly fast F2 lens (same as RX1) and the D750 (with interchangeable lenses) can go to F1.4 and beyond. Of course that is an apples to oranges comparison (smartphone vs. DSLR).
Now, you may be wondering why a phone like the Samsung Galaxy S7 or the iPhone 7 also has superior low light performance compared to the Moro X Pure… the answer again comes down to sensor size and density, the Moto has a 21MP 1/2.4″ sensor paired with a F2.0 lens whereas the Samsung has a 12MP 1/2.5″ sensor paired with a F1.7 lens and OIS. The less dense sensor allows for significantly increasing the sensor sensitivity in dark settings with less noise. Likewise, the additional light gathering of the F1.7 lens helps a bit as well, lastly the OIS (optical image stabilization) really pays off in still scenes by allowing longer exposures (letting in more light). Apple went with a similar approach for the iPhone 7, with a 12MP sensor with f/1.8 lens and OIS.
So, while the Moto X Pure can output some very detailed images in bright situations, it will likely struggle vs the lower MP competitors when it comes to darker scenes.
Lastly, there is something to be said for software optimization. I would say that Google and Apple are at the forefront here, with Samsung following behind and Moto a little further back. You can find some discussion of this here and other places:
But the general consensus is that as software improves and HDR/multiple exposure combinations keep getting better, that software (or even AI) may be able to work some magic even within the limitations of small sensor phones.
Sorry for the long reply, but I thought you had an excellent question!