Flashlight "Throw" or angle of lit area

Is there a term you guys use to refer to the narrowness or wideness of a flashlight beam? Throw? Field angle (like binoculars)?

The reason I ask is that last night I took my brand new U2 and my 1 MM CP hand-held spotlite outside. I shined them both on the woods about 100 feet away.

The U2 made a very evenly-lit circle that was HUGE. I'd say it was 40-50 feet across. Then I used my 1 MM light -- the main "beam" lit up an area concentrated that was maybe 10 feet or less. A HUGE difference.

Now, I should say that the 1 MM light beam was the main light I saw when I shined it on the woods. I also noticed, especially compared to the U2, that there were "light rings" that shown on some trees much closer to me. When I shine this spotlight in the house, I see rings ouside the main core beam (which is the one that was creating the 10-foot diamater lit area 100-feet awy on the wood). So I guess when those outer rings can hit something further away than a wall in my house, but closer than a distant object, they're visible. Like I said, I saw their outlines on some trees that were 20-50 feet between me and the woods.

My 1 MM light is about 12-cm across, has that nice concave silvery mirror surrounding the bright (xenon?) lightbulb in the middle. My U2 is LED and is about 3 cm across.

Can anybody explain what I am seeing with the differing narrow/wide beams of the lights, the light circles from the spotlight (which are tough to see if they don't bounce off something in the foreground compared to the more distant area you are targeting), etc?

In a nutshell you are seeing the effects of different focusing and optical design between two lights.

The rings will appear because the reflector projects an "image" of the light source out the front. Smooth reflectors give a truer representation of that image, "warts and all," as they say. Any imperfections in the source (bulb or LED) are projected out and usually end up as rings. This is also why some LED lights have a squarish hotspot -- it is an image of a square light source.

Bumpy or "textured" reflectors screw up that image and give you a nice even beam, with all the imperfections blurred together.

Some lights have a narrow beam, some have a wide beam. Generally there are two areas, the bright hotspot and the spillbeam outside of that. Often times manufacturers will take advantage of the fact that this is difficult to describe and rate their lights by brightness. You can have a very tight beam that is very bright (that's what gets the beam to "throw" far), but has just about no light in the spill area of the beam. Brightness is measured in lux or candlepower, and really doesn't have much to do with how much light is put out. Total output is usually measured in lumens.

You can't tell a lot about a light given either brightness or total output. You might have a high total output, but that doesn't tell you how tight the beam is. You might have a brightness number, but that tell you neither how much light is given nor anything about the spillbeam. That is why everyone wants beamshots with known lights compared to the light in question.

I hope that helps some.

Scott