Git2P fine focusing (by lens screws)

nekodrugi

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I just managed to fine focus my Git2P (the 90deg) :)
The camera was focused in the center, but top-center and top-left of the image were soft.
Just to make it clear, we are speaking about pixel-peeping at 100% in full res photos.
It is possible that this would not be an issue in videos.
Well I do photos a lot and this irked me.
Today I managed to fix it partially.

I completely opened camera (see one of those disassembly videos).
Lens was not touched (not rotated as one does for typical focusing after e.g. lens replacement).
What I did is to tighten a bit one screw on the back of the sensor.
The back of the sensor has only 2 screws, one top and one bottom.
My reason was that top-center is soft, thus maybe I should tighten the bottom screw.
This was actually hard and I did apply quite some force to tighten it by about 45deg.
And it worked. Not perfectly, but it did improve the image.

Now the old question: do I open Git2P again and again risk it. Not sure...

This is not the first time I am doing this. I also did such fine focusing on my Xiaomi Yi (the original old camera: one of the best for photos if you ask me).
That time I made it more careful and in couple of trials.
And result was that one of the screws I did tighten by about 45deg
(I think there were 4 screws holding sensor for Xiaomi Yi, contrary to 2 screws holding lens base for Git2P).
The improvement was quite significant, but it looked kind of tread-off: the center was touch softened by making 2 edges sharper.
Thus this time with Git2P I just did 45deg tightening on one screw (think which one you need if you replicate this: the bottom or top!).

Anyway, maybe this helps somebody. If really needed I could add some documentation images I made.

My quest now is how to improve the look of the Git2P JPG images.
I don't have time to fiddle with RAW images at the moment so it has to be JPG.
I applied Git2P 90 firmware mod and it did improve details in JPG image:
Code:
https://dashcamtalk.com/forum/threads/git2p-90-firmware-mod.35760/
Now, how do I get better colors and metering in photos? Any thought or your settings are appreciated.
 

Nigel

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If you had to use a lot of force, it may have been better to release the other screw by 45 degrees...

The Git2 is not bad at metering and colours, if you really want better then use the raw files, it doesn't take long
once you know what you are doing.
 
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nekodrugi

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If you had to use a lot of force, it may have been better to release the other screw by 45 degrees...
Not sure. I did used some force, but I wouldn't say "a lot".
My guess: releasing other screw would probably mean that the lens has to be refocused (rotated a bit, probably by smaller degree) for best results.
I think that sensor-to-lens are not perfect planes in any case.


The Git2 is not bad at metering and colours,
Hmmm.
Well, the custom firmware mod from above did improved JPG details, but I think it also worsened colors.
 

Dashmellow

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The Mobius 1 camera had a similar problem with the original C lens module. The problem, which was fairly widespread, was caused by a warped sensor plate that would become slightly deformed as the sensor heated up. The wide angle "C" module was eventually discontinued and replaced with the C2 module which has a much thicker backing plate for the sensor that resists warping and acts as an improved heat sink.

The solution for the C module left, right side or corner focus issue was similar to your technique with the Git2 90º lens module, except that the C module has four screws, one at each corner. The problem is that simply loosening or tightening one of the screws could be problematic because even though adjusting the alignment of the sensor and the lens axis appeared to initially solve the problem, it would reappear eventually as the sensor and sensor plate heated up during camera operation. A loosened screw for example could allow for movement of the plate during expansion and contraction due to temperature changes.

What was required was the use of a shim carefully inserted along the edge of the sensor between the sensor plate and the module housing and then re-tightening of the previously loosed screw. Some trial and error was required to find a shim of the correct thickness to resolve the focus issue. Thin plastic or a piece or two of paper of the proper thickness worked best. Sometime tightening one screw and loosing one of the others with shims in appropriate positioning was required to achieve the flattest plane of focus.

If you continue to experience this problem and find that it eventually goes out of alignment again you might consider trying a shim so that the adjustment you make will be more secure and permanent.
 
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nekodrugi

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The Mobius 1 camera had a similar problem with the original C lens module. The problem, which was fairly widespread, was caused by a warped sensor plate that would become slightly deformed as the sensor heated up. The wide angle "C" module was eventually discontinued and replaced with the C2 module which has a much thicker backing plate for the sensor that resists warping and acts as an improved heat sink.

The solution for the C module left, right side or corner focus issue was similar to your technique with the Git2 90º lens module, except that the C module has four screws, one at each corner. The problem is that simply loosening or tightening one of the screws could be problematic because even though adjusting the alignment of the sensor and the lens axis appeared to initially solve the problem, it would reappear eventually as the sensor and sensor plate heated up during camera operation. A loosened screw for example could allow for movement of the plate during expansion and contraction due to temperature changes.

What was required was the use of a shim carefully inserted along the edge of the sensor between the sensor plate and the module housing and then re-tightening of the previously loosed screw. Some trial and error was required to find a shim of the correct thickness to resolve the focus issue. Thin plastic or a piece or two of paper of the proper thickness worked best. Sometime tightening one screw and loosing one of the others with shims in appropriate positioning was required to achieve the flattest plane of focus.

If you continue to experience this problem and find that it eventually goes out of alignment again you might consider trying a shim so that the adjustment you make will be more secure and permanent.
Very interesting!
Also that is why I tried to avoid loosening screws.


But in general this slight misalignment of sensor and lens must be much more frequent. With me it is both Xiaomi Yi and Git2P.
It is just that it is on pixel-peeping level, and probably doesn't strike in videos and thus rarely anybody bothers. And maybe it is also hard to see in 170deg cameras (and Xiaomi is narrower than that).
Before buying Git2P I did download bunch of full res JPGs on the net for few 90deg cameras and there were some that were sharp, but there were also some with soft pixels in some part of the image.
 

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