Pro Focus LLC | 02/19/17 12:51am
Trying to spec a PTZ for a project and need some info from people who have possibly been down this road before. My concern is that the PTZ I am planning to use is the Hikvision DS-2DF6236-AEL and it has a ƒ/1.5 rated lens at wide setting, but it drops to a ƒ/3.4 in tele mode (36x or 205mm). This is a Darkfighter model that is rated to cover down to 0.002 lux in color (let's assume they are accurate for this discussion) with the ƒ/1.5 rating. I have seen other fixed Hikvisions with less favorable ratings and they were appropriate for this scene.
So, my question is, how can I calculate or estimate the amount of light needed when the PTZ is zoomed to the max 36x (ƒ/3.4)? Is that something that just needs to be done in person and on site for evaluation, or is there math that can tell me my sensitivity loss with the given ƒ/values?