dahua focal length vs fov - what is the truth

[Engee]

Hi Guys,
I hope you will help me.

on Dahua WIKI:

Troubleshoot/What Is Focal Length Aperture Gain Angle of View - Dahua Wiki

• 
  
• 
  2.8mm Lens = 89.9° Field of View
  
  
  
• 
  3.6mm Lens = 75.7° Field of View
  
  
  
• 
  4mm Lens = 69.9° Field of View
  
  
  
• 
  6mm Lens = 50° Field of View
  
  
  
• 
  8mm Lens = 38.5° Field of View

But on Aliexpress stores, even on ANDYs site, there is smth like this:

@EMPIRETECANDY

Focal Length
2.8mm (3.6mm,6mm optional)
Angle of View
H:110° (87°, 51°), V:58° (48°, 30°)

So question from me is, what mapping (focal-length vs aov) is valid?
The differences are too big to ignore.

Thx in advance for help!!!

 

[tigerwillow1]

Others know more about this as me, but as a first input I believe the sensor size is also a variable. I didn't see a sensor size mentioned in the wiki, so I'm taking it as a "representative example". Hopefully Andy's specs are correct for the specified camera. I'm always suspicious because there are so many incorrect specs posted.

 

[tangent]

yep, sensor size is the missing variable.

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[tigerwillow1]

I see I posted to this thread 4 years ago and have learned more since then. The sensor sizes are converted and rounded, and I suspect that Dahua is normalizing the focal lengths for different sensor sizes. I have about a half dozen camera models, so can't make a huge generalization. I've measured their FOV and found that calculating the FOV from sensor size and focal length is fruitless, and Andy's FOV specs are right on within the precision I'm able to measure with stakes in the grass and a protractor. (I measured only horizontal FOV).