Variofocal lens for action camera

Good afternoon (optional evening / night).
Today we look at the lens, which allows to expand the scope of action-camera.
FOREWORD
I own the Eken H9 camera, one ofthe very first installments (who would be interested in firmware 160309LY). It serves faithfully, in general, I am completely satisfied with its quality, but the angle of the lens did not suit me, for me over 100 degrees seemed too much. The camera is filmed, as well as action, and family video, including all sorts of analyzes and rations for customers.

In general, this lens was purchased for the occasion, I picked up from a small angle, and here is a variofocal one, which allows changing the angle and distance to the object, so I decided to take it.
This type of lens is very popular in video surveillance, it happens that photographers enthusiasts buy to get an “interesting” picture or, as in my case, to play.
As usual warning:

All responsibility, namely independent penetration into the body of the finished product with the subsequent violation of its integrity of efficiency, lies with the person who committed this action.
Appearance and Measurements
Characteristics of the lens from the seller:
Model: M12-02812-3MP-C-FL
Mount: M12
Resolution: 3 megapixels
Image form 1/2. five"
Focal length: 2.8-12 mm
FMS: 6.0 mm
BFL: 7.7-13.9 mm
BFL flange: 13.5 mm
IRIS: fixed
M.O.D .: 0.3 m
Weight: 33 g
Dimensions: Φ28 × 40. 1 mm
Optical distortion: -59.4% ~ -5.1% (1/2. 5 ")
Field Angle DxHxV (°): 135 ° X108 ° x81 ° (wide) / 43.4 ° X34. 7 ° X26 ° (Tele) (1/2. 5 ")
Operating temperature: -20 ° C ~ + 60 ° C
The lens is made of metal and has lenses of glass, which is important in the transfer of the image.
Designed for M12 threads, has a built-in IR filter and this is also important.


As a rule, the variofocal lens is essentialsmaller in size and cost than a zoom lens, a simplified version of which it is. The focal length of the variofocal lens and the viewing angle are adjusted manually by rotating a special ring on the body. This allows you to accurately set the required angle of the field.
The outer ring allows you to adjust the sharpness, the inner ring allows you to change the angle and thus the distance to the object


In this image, you can estimate the difference in the sizes of the two lenses.

Using the classic table for testing angles, you can get the following results (rather coarse, but similar to the truth)

I apologize for the quality of the tested table, low resolution, printed on A3.
In widescreen mode, about 95 degrees:

In the body mode about 40 degrees:

Disassembly
Understanding the lens is quite simple.
1. Remove the brass snap ring:

2. Carefully lift the inner adjustment ring:


3. Then remove the ring securing the lens in front:


4. Remove the lens:

And immediately below it the second:

In general, that's all, I took it down first of all to remove this dust, well, and show you:

As you can see a primitive device, inside everything is smeared with sticky grease, similar to Mobil blue grase.

Installation in the camera
The camera is installed without any problems (in my case), the decorative ring is removed and the old lens is unscrewed:

I do not know how in the new versions of the devices, in my presence there is a metal fastener, on which it is so easy not to break the thread.
The lens is screwed in as far as it will go, it will not reach the matrix and will not scratch it. Also the seller together with the lens puts in a package with a locknut.

In these photos, you can evaluate how the lens is installed in the camera:




The gap between the lens and the camera is minimal.
Shooting examples
As examples, let's start with macro photos:



Macro shot from a distance of 10 cm, which is quite a good indicator, you can quite clearly do the inspection of the board and even solder by connecting the camera to the monitor.
Next, we will look at one and the same picture with body presets and wide-angle:
Tele:

Wide angle:

Video with an example of the lens:
At night:

Happy:

Results
I really liked the lens, there are no minuses as such, it completely met my requirements.
The main disadvantage is that the characteristics of the seller are slightly incorrect, but this is the lot of almost all the optics on Ali. Although maybe I'm wrong and knowledgeable people will correct me in the comments.
Update:
In general, suitable for any camera with M12 mount, the diameter of the hole for the lens - 20mm should be.

Update 2:
An example of connecting to a TV via HDMI: