What causes fixed-cam to go out of focus 2-year later?

I have 5 fixed Dahua (Amcrest) 3MP bullet cams. They are the IP3M-943 which is a 3MP fixed cam. They are Dahua based and are about 2 years 6 months old.

Anyhow, 2 of them out of the 5 started to develop blurriness in the background. Anything beyond 20ft+ it gets blurry. License plates begin to look like cock-eyed image where you have two overlapping on top slightly.

Is this because the camera is exposed to UV?

I have removed the cameras in question and cleaned the lens housing both inside and outside with isopropyl alcohol 70% and that seems to clean up the haze and image is sharper up close. But the blurriness did not go away overall. The other 3 cameras do not have this problem.

Anyone know why?

Are the ones with the issue facing the sun?

If so could be long term heat shifting (ie expansion when hot and contraction when cold) ever so slightly adjusting the focal point of the lens.

The lens are usually screw in - you can normally remove the existing glue (if any) with a heat gun / hairdryer and then just refocus correctly by very small movements left or right - always mark the starting point using something like a Stanley knife (hobby / craft knife maybe in the USA?) as you're talking potentially an adjustment of a degree or two.

It happens a lot more with dashcams as they usually get hotter in closed cars, and the same problem happened with my Ring Pro doorbell which had to be replaced as over time the focus shifted and the default was out of focus. It took weeks of support time to persuade them to send me a new one so I jumped over to Nest Hello as soon as I could and have never seen the problem since.

Back in the dashcam days sometimes plastic lens mounts would also cause a similar problem so the higher end cameras used metal bases.

Yes, both the cameras affected are east and west facing and could be under direct hot afternoon sun. The rest of the cameras are at different offsets, more SW and NE.

MakeItRain said:

I have removed the cameras in question and cleaned the lens housing both inside and outside with isopropyl alcohol 70% and that seems to clean up the haze and image is sharper up close. But the blurriness did not go away overall.

Click to expand...

Take a close look at the lens itself under a magnifying glass, moving it around in bright light so you can see reflections on the surface.
You might notice that the surface is a little hazy due to deposits from volatiles in the case.
The lens itself can be carefully cleaned using IPA or window cleaner and a soft lens cloth (not a Q-tip, they can be harsh and oily).

alastairstevenson said:

The lens itself can be carefully cleaned using IPA or window cleaner and a soft lens cloth (not a Q-tip, they can be harsh and oily).

Click to expand...

FWIW, I now have only the automotive glass cleaner in the house, it has no ammonia, uses alcohol instead and isn't harmful to plastics. I use it on TV, monitor and laptop screens (spray on cloth not on screen). Armor All and Turtle Wax make it.

MakeItRain said:

I have 5 fixed Dahua (Amcrest) 3MP bullet cams. They are the IP3M-943 which is a 3MP fixed cam. They are Dahua based and are about 2 years 6 months old.

Anyhow, 2 of them out of the 5 started to develop blurriness in the background. Anything beyond 20ft+ it gets blurry. License plates begin to look like cock-eyed image where you have two overlapping on top slightly.

Is this because the camera is exposed to UV?

I have removed the cameras in question and cleaned the lens housing both inside and outside with isopropyl alcohol 70% and that seems to clean up the haze and image is sharper up close. But the blurriness did not go away overall. The other 3 cameras do not have this problem.

Anyone know why?

Click to expand...

which dahua firmware for that amcrest model?