I’m trying to use imageJ to overlay two pictures and find the shared void area. When i use the merge channel function to make a composite picture 3 from pic 1 and pic 2, it gives me all the void from picture 1 in red and picture 2 in green, and the shared void area in yellow. Then u convert it to black and white 8-bit, which generates pic 4. However, the void (black area in pic 4) are the summation of red, green and yellow. Is there anyway to make the yellow part of pic 3 the only black area in pic 4?