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?


According to our F-Stop Calculator, it is just over a 4x reduction in light sensitivity:

I'd still field test if there is any concern about low light performance. When zooming far out / looking at objects far away, more factors / issues can come into play.

So what does that mean to the 0.002lux rating though? I don't think that means 0.008lux....

In our testing of many, many cameras, lux ratings are never applicable to real world conditions, meaning if you took a lux meter on site and it registered the lux level that the camera specified, the camera would capture a completely dark and unusable image. Don't Trust Lux Ratings

Have you measured the lux levels of both the area close to and farthest away from the camera that you intend to monitor? You may find that one of those two areas has far less light than the others and this will come into play as well.

Yeah I get all of that. I am saying, from one mode to another in Hikvisions lineup, I SHOULD be able to compare apples to apples the lux levels. I wouldn't bet me life on it, but you would hope that the worldwide leader in security would be able to have a testing standard for their spec sheets.

That said, I would never compare between brands, where standards could be way different.

So back to my question, is there a mathematical way to compute the lux level sensitivity of the camera at its tele f stop? I am willing to accept a no answer, I just am outside my zone here.

is there a mathematical way to compute the lux level sensitivity of the camera at its tele f stop?

Yes, I gave that to you above and copied below:

All I am saying is that other factors could materially impact how good or bad the actual performance the camera delivers at the far end vs the near end.

In other words, 4.14x is the 'math' but the 'math' only factoring in the f stop differential. All factors will impact actual field performance, ergo why field testing is important.

"I wouldn't bet me life on it, but you would hope that the worldwide leader in security would be able to have a testing standard for their spec sheets. "

Jon,if you ever find testing standard/procedure for any manufactures

I would be happy to hear :)

I mean for IP cameras only

Jon,if you ever find testing standard/procedure [for lux] for any manufactures...

Related: Manufacturers: What Is Your Method For Calculating The Dynamic Range Of a Camera?