Anyone changed a camera lens with one of a different focal length?

Suppose I wanted to change the M12 lens mounted on a Hikvision 3MP mini-bullet, a DS-2CD2035FWD-I with one of a different focal length, there are lots of M12 lenses for sale on eBay. Has anyone done this sort of thing? No change is not a big deal here, but I'd just like to know what options might be possible in the future.

I've not done it on that particular camera but generally you can. Assuming that it fits and differences in lens quality aside, then the biggest issue that I've had is getting the focus right again. For some the tolerance for being in/out of perfect focus is ridiculously tiny. Like a few degrees/1 mm of a turn and then when you tighten things down again it will change or move with temp, etc. Don't want to make it sound harder than it is, but sometimes will drive you nuts trying to get it exactly right. Really better to get a variable focus camera from the start and not have to deal with it.

Edit to add: I should have said variable auto-focus. The manual variable focus cams can be even more frustrating trying to get just right with two adjustments.

@toastie Yes, it's been done before, at least with Hikvision turret. Read this thread:

Change a Hikvision lens from 2.8mm to 4mm or 6mm?

There should be a YouTube video too.

toastie said:

Has anyone done this sort of thing?

Click to expand...

I've changed maybe half a dozen lenses, mostly Hikvision.
There is a bit of uncertainty the first time, but after that no worries.
One of the important things to watch is avoiding contamination with dust or debris, not leaving the sensor exposed upwards for example.
And keeping your fingers off the lens.
I've been pleased with the products from here : TREEYE Official Store - Small Orders Online Store, Hot Selling and more on Aliexpress.com