Question about LED throw

[kantonburg]

I'm sure this is a completely newb question, but last night I was toying around with my Taskforce 2C CREE and when I stuck my finger in front of the lens I noticed that the hotspot on the wall didn't change. It just got about half as dim. When I removed my finger the shape on the wall didn't change it just brightened up. It's not like there was a spot on the wall with a shadow from my finger. You couldn't even tell my finger was in front of the lens. I mean right up against it.

Why wouldn't my finger show up as a shadow? Sorry if this is a dumb question, but as my title says I'm unenlightened.

 

[Sir Lightalot]

because the light that makes the hotspot doesn't just come from the center of the flashlight, it comes from what bounces off the reflector and angles toward the center...if that makes sense.

 

[divine]

Have you noticed that shadows are typically blurry? Because light doesn't come from a single point, and how big the source of the light is effects the shadow...

If I hold up my hand between you and a light, and the lamp, or lamp and reflector is 6" wide, my hand might be blocking the left side of the light and not the right side of the light.

Also, we're not using perfect reflectors, notice the spill... so the light is coming out at different angles. In your case, the light is getting angled around your finger.

 

[kantonburg]

I kind of thought that was what was happening. I just thought there would, at the very least, be a faint shadow of my finger. I suppose it's not important.

On a side note, being this is my first LED. I have a nice bright hotspot, then a small ring, then some corona, and some spill. My concern is the ring thats between the hotspot and the corona. Is this normal?

 

[carmatic]

what is happening is that for every spot on the wall that you are shining at, the light came from all over the reflector... so if you blocked the light from a section of the torch from reaching the wall, that particular spot on the wall will still be lit by sections of the reflector which you did not block... think of it as light from all across the front of the reflector travelling in slightly different directions, and light from all over the reflector will end up on the same spots on the wall, and because the reflector is larger than your finger , it sends some light 'around' your finger to light the wall 'directly behind' it...
basically , your finger is leaving a shadow that's so blurry that it made the whole beam dimmer

but if you held your hand in the spill, you will see a clear shadow because it is the light that is coming straight from the led, which is alot smaller than the reflector, and alot smaller than your finger, so its not big enough to blur your shadow too much