How to determine a fixed focal length using a variofocal 5442?

[ipmania]

Noob here. I have been tinkering with 5442 variofocal turret. I'm not at home right now but if I remember correctly, the zoom range setting was a slider.

I'm wondering how I could determine which of the 2.8 or 3.6 or 6mm lenses would be the most appropriate by using the varifocal camera.

 

[Alaska Country]

There is a calculator on this site that will assist with your needs.

Focal Length Calculator

Calculate the focal point of a camera to help determine the best size lens to order. Save & view your results later.

ipcamtalk.com

Make sure that the sliders are set from their default settings of 20 to 1 for zoom and focus. If you have not found it already, just mouse over the slider tap for the number setting.

 

[Alaska Country]

For the turret 5442-ZE (2.7 - 12mm lens) the focus maximum steps is 2275. To find this number, the simplest way is to change the zoom speed from 20 to 1. Then move the tab to the right as far as it will go. That mouse over number will be the max steps for the camera zoom.

The other way is to use the Dahua API and extract the data for each camera of interest.

http://admin:password@192.168.55.50/cgi-bin/devVideoInput.cgi?action=getFocusStatus

status.Focus=0.610922
status.FocusMotorSteps=2930
status.LenAdjustStatus=0
status.Status=Normal
status.Zoom=0.285275
status.ZoomMotorSteps=2275

From the API data to determine the tab number Zoom x Zoom Motor Steps. Or 2275 x .285275 = 649.

Placing these number in the above calculator the set point for the desired lens focal length is as follows:

2.8mm - 24.5
3.6mm - 220.2
6.0mm - 807.3
10mm - 1785.8

Note that a 6mm lens on different sizes of sensors will produce different FOVs.

 

[kobebeef]

What is the focal length in mm?

 

[wittaj]

What is the focal length in mm?
View attachment 157807

Since the zoom is 0 that would be whatever the smallest focal length is for that camera.