Just finished a sub zero test on my optics! 8 hr in negative temps. It was my yearly battery swap so I thought what the hell. So I turned both my DR & my T-1 to max and set them out in the snow & ice. After 8hrs both the Elcan and the Aimpoint were still working. The Elcan was dim but still visible, the 1-4 worked fine. The T-1 was still blazing away with no noticeable change. Both QD (arms bobro) still worked fine. The intensity selectors where both noticeably tighter. All in all I think both did well! :?