Hmm?!
On any dahua camera lens and leds are seperate. mostly they dont even share the same protection glass in the front of the housing. leds are mostly glued into the front cover and the lens(front) is inside a piece of/covered by sponge rubber. so its not even possible that light from the leds shine into the lens from inside the camera housing.
i dont get your problem...
That's not separate if they're built into the camera face. They're too close to the lens. If any light spills either onto the lens or if there's atmoshperic particles such as mist, fog, dust (no matter how little) and it lights the atmopshere ahead of the lens, you'll get bloom or a haze to the picture.
When I say separate, I mean no LED on the camera and a separate flood light elsewhere on the wall. Theoretically, Dahua could mount an led on an adjustable bracket on the top of a bullet style housing provided the lens was hooded and shielded from the light. The light would also need to stand high enough so as not to cast a shadow on the main viewing area caused by the camera housing. However, it mgiht look cheap and by far the best way to do it in my opinion is have a camera without LEDS and a separate Spotlight with PIR on the wall a good distance away and not pointing towards the camera. Although most CCTV cameras seem to adapt almost instantly these days to light changes, if you wanted to reduce the impact if the area has no ambient light, no reason why you couldn't have a low level dawn to dusk light eg 6w led bulb giving permaent low level light but reinforced with the flood. That way the camera isn't having to adapt from nothing to ultra bright but equally should have enough light for a good picture when the flood comes in.