We have seen several domes from Dahua have IR bounce back. I know its more common with domes, but is it normal to see it on most of the domes installed, or is it just manufacturer/model issue? We have not tried any other manufacturers yet.
We are using bullets and turrets moving forward.
That is what you get for using Dahua but no this is not common in better cameras.
I employ many hikvision minidomes with integrated IR and have never had this problem.
Always make sure to wipe clean in and outside the dome. Nothing wrong with Dahua quality, domes in general "can" be susceptible to bounceback. I always do bullets whenever possible.
those are more than the typical IR smear and haze you get when ir gets trapped into the polycarbonate material and travels sideways, like a fiber optic cable.
but those reflections almost look like bokeh.
and it’s not even totally dark in the scene either.
which model is it exactly? so we can look at the lens separator etc...
On the odd occasion that this has occurred, I personally have found that the dome is not properly "seated" or that the shroud has been removed. Otherwise, I never have this problem.
On the dome cameras we use, there is a foam seal around the lens that separates the lens from the IR LED's so this doesn't happen. 
I have found that when you use a wide angle of view with a dome with internal IR, you get this IR bounce back more.
I decided to switch to turrets and bullets and now have nice clear night time images.
We still use domes outdoors for lower mounting height positions. We use bullets for higher mounting positions. Turrets are used when there is no good alternative and wall mounting is preferred. Domes always get a wall mount bracket. No one should ever mount a dome flat on the building with the back of the dome vertical unless it has a sun shield specifically designed for such use like the one Axis has and Hikvision has. Eventually the dome will get destroyed by UV and that little but of IR reflection will be much worse.
Indoors, you shouldn't have a problem. What model is the Dahua camera? On brand new installs of Dahua I haven't experienced that issue. You must always be careful with the dome as any scratches in the dome will cause reflection issues. The same is true for the other points made in this thread.
The cameras on my house in the soffitt only get reflections when the dome get dirty. At that point I just walk around with the DomeWizard and they are generally good as new in a few seconds without getting a ladder out.
I will deal with most of the issues connected with domes because they simply look the best and it's more difficult to knock them out of position. With newer super low light cameras, you generally can get by in full color with just a little bit of security lighting. Then the IR reflection issues becomes a non issue.
The camera is from ENS, a Dahua OEM HNC5V261E-IR-ZE
This one is a 6MP varifocal dome
We have 2 of these there and both are doing the same thing. As mentioned, its not even that dark in the posted image. In darker scenes it is worse.
Here is the same model at a different site. You can see issue ever so slightly but not enough to be a problem.
The first camera is only 3-4 months old and probably had the issue from Day 1. My tech has cleaned the dome, rotated the dome, put the dome on carefully etc.
I wonder if one camera has the lens pointed up higher, and that is causing the gasket not to seat properly?
Make sure the foam/rubber ring is contacting the inner dome surface. These are generally spring loaded and delicate. It may be that the first dome has a factory fault with this mechanism.
These types of issues are why I have started trying to avoid IR in general. With the low light color capabilities of today's cameras, we no longer have these IR issues. Its time we all move past the days of IR and its shortcomings. Monocrome images, reflections, etc. If you put that same camera in color mode, those reflections go away 100%. This camera has a STARVIS imager, which performs well in color in low light. Give that a try in this scene and see how well it works out. Make sure to test for motion blur too.
Dirt, pollen, dust sitting on the exterior of the dome are usually the culprit. HOWEVER it also depend on how the IR is built into the camera...if it is built into the body of the camera, and not immediately surrounding the cameras eye, you get better results. Typically any dome with a physically boardered separation of the IR from the eye. Hiks new 4MP ptz does well at this.
The only time I've seen that is when my installer forgot to put the rubber ring on the lense. (Axis P3225)
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