I also have another image captured at 0.7ms with Gain24. (I2) (As attached) This image has both noise and signal together.
I would like to compute SNR value by calculating the variance of the signal I1 and variance of noise (I2-I1). Since the gain and exposure are different, the pixel intensity of my I2 image is different from I1, such that (I2-I1) gives not only noise but also a considerable amount of signal.
Is there a way to only compute noise variance from I2 to find SNR. Which also means is there a way to find the true signal in I2