New 108MP does not work with ISO>100 (Redmi note 10 Pro)

[xseryd]

Hello,

I noticed that the 108MP does not work with ISO>100 on the Redmi note 10 Pro. Affected are both the standard 108MP mode as well as the Pro mode with 108MP turned on. With "does not work" I mean that the resulting photo with ISO>100 (e.g. 125) still has 108MP resolution, but it is fake - it is just upscaled 12MP to 108MP.

I attach only small crops from the 108MP photos, because the originals are too large to be uploaded (101_cr.jpg uses the real 108MP, 112_cr.jpg the fake 108MP).
Photo settings:
- Both photos taken about 10s apart, with the same lightning conditions
- Both photos taken with the stock camera using the pro mode and 108MP mode
- Both photos taken with all the settings automatic except of using a fixed ISO (100 ISO and 125 ISO)
- Both photos taken using a tripod and 2s self-timer to avoid camera shake

Several notes to the behavior:
- When I manually upscale the 12MP photo in the PC I get the same result as the "108MP" fake photo.
- When the fake 108MP is active, the photo is taken very fast (<0.5s), whereas when the true 108MP photo is taken it takes about 1s-2s for the photo to be taken.
- The real 108MP file is usually a lot bigger than the fake 108MP (attached originals are 22MB vs 14MB)
- The real 108MP tends to have a greenish tint
- The fake 108MP is oversharpened, even when viewed zoomed out - exactly like the 12MP photos
- I know that the quality of the photo should decrease with increasing ISO, but the decrease should not be this sharp. Moreover, the quality is almost the same for ISO 50-100 and then for 125-500, the sharp jump is only at ISO 100.
- I reported the issue several weeks ago using the phone Services and feedback function, but have not received any feedback yet.
- Even with ISO <= 100 the real 108MP photo is not always captured - I did not find the reason for that yet. It seems to do with the lightning conditions.
- I tried reseting both phone and camera cache - did not solve the issue
- I use MIUI Global 12.0.13 Stable version. Previously I had some earlier version, which showed this behavior as well.
- I tested this on 2 Redmi note 10 Pro phones, both behaved exactly the same.

I love the potential of the 108MP photos, with it I can do some cropping even on 4K monitor, therefore I would really love to use them. Unfortunatelly It is quite hard to do so. The worst think about this issue is that even with ISO <= 100 the real 108MP is sometimes not taken and therefore I cannot compose the photos as I would if the 108MP would be reliable.

Thanks a lot for support.

 

[dexterv]

Well this makes sense when you think about the technology. Bayer cams bin pixels together to simulate larger pixels so that they can absorb more light. When increasing light sensitivity requirement you want the sensor to get more light and it does by binning it cannot get the same amount of light from the small pixels. This is just my explanation though, don't take it as cannon.

 

[xseryd]

Well this makes sense when you think about the technology. Bayer cams bin pixels together to simulate larger pixels so that they can absorb more light. When increasing light sensitivity requirement you want the sensor to get more light and it does by binning it cannot get the same amount of light from the small pixels. This is just my explanation though, don't take it as cannon.

I would hope that the 108MP would work regardless of the ISO but it would be more noisy. Then e.g. at around ISO 400 or 600 it could happen that the 12MP photo would look better, because the noise would be already too high in the 108MP.
As the phone allows usage up to ISO6400, (even more in automatic mode) I think 6400/9~700 could work in the 108MP mode.