In the application of remote sensing cameras

the grayscale distributions of the transferred images are normally bad. In order to solve this problem

some researches are carried out. The factors that affect the grayscale distribution are analyzed

and three methods are proposed for background subtraction and grayscale stretch based on the parameters of remote sensing camera's imaging electronics. The richness of gray levels of the three methods is formulated

and the optimal method is given. That is

analog stretch is implemented together with digital stretch and all the processes are based on the images with original bits of ADC. Then the lowest some bits are abandoned

and the images with the remaining bits are transferred down to earth. The experiments are made based on an actual remote sensing camera's imaging electronics system in laboratory. The results indicate that the proposed three methods can all achieve the functions of background subtraction and grayscale stretch. The third method brings more gray levels to images than the other two

and leads to better imaging quality. Further

it can be applied in the remote sensing cameras.