Hikvision Darkfighter PTZ - Lux Level / Sensitivity Wide Vs Tele?

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?

Login to read this IPVM discussion.
Why do I need to log in?
IPVM conducts unique testing and research funded by member's payments enabling us to offer the most independent, accurate and in-depth information.

********* ** ****-**** **********, ** ** **** **** * ** ********* ** ***** sensitivity:

*'* ***** ***** **** ** ***** ** *** ******* ***** low ***** ***********. **** ******* *** *** / ******* ** objects *** ****, **** ******* / ****** *** **** **** play.

** **** **** **** **** ** *** *.****** ****** ******? I ***'* ***** **** ***** *.******....

** *** ******* ** ****, **** *******, *** ******* *** never ********** ** **** ***** **********, ******* ** *** **** a *** ***** ** **** *** ** ********** *** *** level **** *** ****** *********, *** ****** ***** ******* * completely **** *** ******** *****.***'* ***** *** *******

**** *********** *** *** ******** **** *** **** ***** ** *** ******** **** **** the ****** **** *** ****** ** *******? *** *** **** that *** ** ***** *** ***** *** *** **** ***** than *** ****** *** **** **** **** **** **** ** well.

**** * *** *** ** ****. * ** ******, **** one **** ** ******* ** ********** ******, * ****** ** able ** ******* ****** ** ****** *** *** ******. * wouldn't *** ** **** ** **, *** *** ***** **** that *** ********* ****** ** ******** ***** ** **** ** have * ******* ******** *** ***** **** ******.

**** ****, * ***** ***** ******* ******* ******, ***** ********* could ** *** *********.

** **** ** ** ********, ** ***** * ************ *** to ******* *** *** ***** *********** ** *** ****** ** its **** * ****? * ** ******* ** ****** * no ******, * **** ** ******* ** **** ****.

** ***** * ************ *** ** ******* *** *** ***** sensitivity ** *** ****** ** *** **** * ****?

***, * **** **** ** *** ***** *** ****** *****:

*** * ** ****** ** **** ***** ******* ***** ********** impact *** **** ** *** *** ****** *********** *** ****** delivers ** *** *** *** ** *** **** ***.

** ***** *****, *.*** ** *** '****' *** *** '****' only ********* ** *** * **** ************. *** ******* **** impact ****** ***** ***********, **** *** ***** ******* ** *********.

"I ******'* *** ** **** ** **, *** *** ***** **** **** *** ********* ****** ** ******** ***** ** **** ** **** * ******* ******** *** ***** **** ******. "

***,** *** **** **** ***************/************ *** ************

* ***** ** ***** ** **** :)

* **** *** ** ******* ****

***,** *** **** **** ******* ********/********* [*** ***] *** *** manufactures...

*******:*************: **** ** **** ****** *** *********** *** ******* ***** Of * ******?