😱 This is incredibly helpful research. Thank you for this!
It looks like the QHY600-Lite is the winner against the ASI6200, due to the slightly lower read noise, higher quantum efficiency, larger image buffer, and higher framerate. I'm not sure why the QE is higher or read noise is lower, I thought these were a properties of the sensor?
And it looks like both have an SDK, which would allow me to use a low-power device like a Raspberry Pi or Jetson as an "HDMI converter": connect to the camera, buffer the images, process them on the GPU, and output over HDMI to an external recording device. This would all probably double our total wattage, which is currently around 25W (camera, gimbal, recorder). This will create a new bottleneck in terms of power requirements, but it would be worth it if the video is less noisy.
Here's one thing I'm still not totally sure about. I've seen measurements of 0.54e- read noise for the highest gain settings on the a7S, but the QHY600 gives 1.1e- read noise at the highest gain setting in the high-gain mode. How can we compare the "overall sensitivity" in a way that accounts for this? Let's say we have 5 photons per photosite (or binned photosite), and ignore dark current. Can we say the following: a7S III SNR = (5 x 65%) / 0.54 = 6 and QHY600 SNR = (5 x 87%) / 1.1 = 3.9
Does this imply the overall SNR of the a7S III should be around 50% higher? Or have I oversimplified things?
One way I can imagine that I may have oversimplified is that the QHY600 sensor may have a microlens array, while a debayered a7S III does not. This could make a big difference in photon count.
Since it looks like the framerate concern is workable, do you have any intuition about this remaining SNR question?
For some context, here is what a raw frame of video looks like from an a7S III (with bayer filter) at 4K f/0.95 1/25" (shot in high-gain mode), out on the ocean in good conditions (SQM-L was reading 21.4-22.2). (This was 2020-06-13 around Hawaiʻi looking towards the West, but I don't remember the exact time.)