## How to calculate system gain, readout noise and full well capacity?

1. Connect the camera to the lens and take two flat field pictures inside the shadowless lampshade. Try to ensure that the brightness of the two pictures is uniform and consistent, and it is recommended to use 1/3 or 1/2 of the saturation value. Here we can give these two photos any name, such as A1 and A2.

1. Open the MAXIm DL software, use the “Pixel Math” function in the “Process” menu to subtract the two images A1 and A2. However, simply subtracting them may result in some pixel values being directly equal to 0. Therefore, add a constant (such as 3000) to the subtraction so that each pixel value is greater than 0. The formula is SUB = A1 – A2 + CON.

1. Select a uniform area on the SUB, please note that this area should not be too large. Remember the coordinates and STD value of this area for the following operation.

1. Divide the STD value you just got by the square root of 2 to get the STD value for a single image. Remember this value.

1. Take an area on A1 or A2 with the same location and size as the area selected on SUB, remember the average value of this area. And then select a black level area at the same level, remember the average value of this area. Subtract the average value of the black level area from the average value of the selected flat field area, and name the resulting value AB.

1. Divide AB by the square of the single STD value, the formula is AB/ (Single STD value)2, we can get System Gain.

1. Take a picture of a dark field (with an exposure time of 0) and remember its STD value. The readout noise is equal to the system gain multiplied by the STD value.

1. Increases the exposure time of the camera until the exposure value no longer rises, at which point the exposure value is the saturation value of the camera. The full well capacity is equal to the saturation value multiplied by the system gain.