I don't have this camera, so can't reproduce your issue but is there an option to select 12-bit mode? Even with the data only using the lowest 12 bits of the 16 bit space, I'm surprised that this couldn't just be stretched.
The Indi driver interface showing it's 12bit ADC and the imaging tab showing I have "mono 16" selected.
The Fits header reads 16Bit image.
And yet the maximum ADU can be taken via the camera does not go beyond 4096.
For example, trying to make flats and I have to select 2000 ADU as the average exposure, even though I'm supposed to be in 16bit mode.
If I try to process it in Pixinsight, Pixinsight cannot plate solve or even detect stars, which otherwise shown in the Ekos fits viewer as well exposed.
Impossible to make flat or bias frames as well.
I managed to stack once with severely over exposed subs of the Andromeda, but after stacking it looked like it was missing several shades of grey, looked like a poster.
This isn't an issue in Windows ASCOM drivers (that has other issues, like black bars around the images) , with N.I.N.A I can expose and save the images in 16bit with max ADU of the 0-65536 range.
I've checked my Meade LPI-GM Advanced (Touptek imx178 rebadge) and see a maximum value of 16k, which matches what you're seeing except that I'm using a 14-bit sensor. I see the same thing with my 14-bit Canon T7.
It seems to me that what you're seeing is normal, or at least, not a problem. I stack with siril so unfortunately don't know if pixinsight needs additional configuration to handle this. It is odd that you don't see this with the ASCOM drivers, though.
Yes, the conversion happens with the ASCOM driver in windows and the images I get are 16bit with a 16bit histogram.
Also another odd thing, the sensor size is 4640 x 3506 inside the Ekos, which is correct manfuacturing spec
With the ASCOM driver though the images are showing 4632x3504 (With NINA and Sharpcap) and I get black bars on the top and the right side and flat corrections just don't work.
That's why I want to use the camera with the Indi drivers and I was hoping there is some sort of settings to make the camera display the images in 16bit correctly and not 12bit. I have to find another way to stack my images, because Pixinsight refuses to work right with the subs taken with the RPi.
BTW, this is the same sensor as the ASI1600MM (panasonic).
I think the problem is, the Fits header reporting "16bit" mode while the actual image is still 12bit.