I am capturing numerous five minute exposures in a completely light free environment with an STF-8300M with active cooling set to 0 °C. When I compare the signal of the images, nearly all of them are within .1% of each other. Occasionally an image is captured that has across-the-board signal loss around 9% when compared to the other images and I need to know why. The drivers and firmware of my camera are somewhat out of date. sbigudrv.dll 4.88 Build 4 sbigu64.sys 220.127.116.118 stf-8300usb.bf2 2.45 stf-8300ga.bf2 2.16 I have not updated these yet because my organization has customers that are experiencing this same issue and I want to understand the problem first. This unexpected signal loss is causing serious problems downstream and any help understanding the issue would be very appreciated.