Interesting thread, lots of good info.
TLDNR: Decent quality separate illuminators are the way to go! Consider output power (strong enough but not too strong), beam angle, placement, and you'll be laughing.
I've experimented (and continue to) with various ways of getting the best night vision for a while, and agree with most of what's been said here.
Agreed too that the big one in your situation is to remove the branches.
At the risk of further repeating what's already been said...:
I've tried many cheap illumniators (via eBay etc) over the years, and they were all worth what I paid for them, not a great deal. They tend to have a central intense hotspot of light, and average wider-angle coverage. And they didn't last very long. About the only use I have for them now is as a source of IR light to bounce off a ceiling in order to get fairly uniform coverage of a small to medium size room. Not relevant in your situation...
Quite a few years ago now I decided to get some decent lights for some specific outdoor locations. I ended up ordering a number of illuminators direct from ParagonTech (the PI-1000 series
http://www.ewhaglobal.com/product/ir-illuminators/pi-series/). I got a range of different beam angles from 15° to 120°, some 940nm, others 850nm. I was so impressed a couple of years later I got more.
This was in the days when the Aussie dollar was worth something, and shipping wasn't so exorbitant (they're pretty heavy). At the time it was also more difficult to find quality IR lights. Pretty much every consumer level IR light consisted of clusters of low power, low quality LEDs as above. There's more choice out there now.
Anyway, some observations. In the vast majority of installs, if possible, using separate IR lighting instead of the camera's built in option is way preferable. When done well (which isn't always easy), the night time views can be many times better than with built-in IR alone.
A separate light can be mounted to illuminate the areas most important to you, you're not stuck with it pointing only where the camera points or with the beam angle built into the camera. The moths, spiders and other pesky critters that make a mockery out of night time picture motion detection are attracted to the light and leave the camera blissfully alone. Because the angle of the light is not in line with the lens of the camera other objects that end up in front of the camera also don't reflect back as much light and trip motion detection (heavy rain being a big one, and just general flying insects).
As others have said, there are a number of important factors to consider when selecting a light and choosing where to mount it.
Ideally the beam angle will match the camera's so you get comprehensive coverage. But you might also choose (as I have in one location) to use more than one light to get maximum coverage. One of my cameras looks down a driveway. It's a pretty wide-angle camera (4mm HikV Bullet), but the illuminator is 15° - the built in IRs illuminate up close, the separate one reaches out down the driveway and into the street (so I still have a problem with rain setting of motion detection, but
most of the insects seem to prefer the brighter light thankfully). In another situation I have a 120° light providing illumination for 3 cameras, all with their own IR turned off.
One common advantage of course is in the situation you have now with the tree. If the tree can't be cut back, the light can be positioned to avoid the tree entirely. I have the same issues with trees, and cars parked in front of cameras which would make the built-in IRs unusable.
If you mount a light right next to a camera, you may reduce the advantage of keeping the flying, web-building critters out of view. If you mount it a long way from the camera, depending on the scene you're lighting, you may create large shaded areas in your camera view.
Clearly you want the light to be powerful enough to cover the area you want to watch with minimal noise etc in the image. However, keep in mind that it's also very possible to have too much IR light. A powerful light might be great at reaching out and seeing medium and long distance objects, but when someone approaches the camera they may well just appear as a totally over-saturated bright white lump, completely unrecognisable. The extent to which this is a problem will vary from camera to camera, some compensate much better than others. My personal preference for a situation where I want to be able to identify faces (and number plates for that matter) is to have plenty of light and to set things such as WDR (which may help or hinder depending on the camera), Gain etc low or off. It means the general scene can be quite dark, but when someone/thing enters the area they are clearly visible, and in good, recognisable detail.
BTW, in many cameras I've found WDR causes ghosting of moving objects. Again, varies from one camera to another.
If you don't want to have too many bright red glowing lights visible at night, consider 940nm. Even in a powerful light it's barely visible as a dark purple glow when close to the light. But keep in mind that you'll need significantly more power/output with 940nm to cover the same area as a less powerful 850nm light. Of course having
some obvious IR lights, and therefore cameras, is generally a good thing isn't it.
I wish I could have separate lighting for all of my cams. There are a couple in particular, under the eves of the house (Hik turrets at the moment), that have great views, and their built-in IR works very well, but the damn spiders and flying fool insects mess with motion detection too much. Lots of surface insect spray helps with the spiders, but not the flyers or course. There's a point though where adding heaps of separate devices (cams, lights, PIR (which I have to experiment with too)) starts to make the place look like a maximum security jail. :rolleyes-new: