Flashlight Focal Length
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Gunner12
Flashaholic
The batteries shouldn't affect the focus length. It should be in the same focus with dead or fresh batteries.
I don't think I have ever seen anyone actually state focus length or how they measured it in a review.
I also don't see why they would include it.
I understand that I could be helpful to determine the minimal distance where you get the correct beam.
Do you mean where the light source has to be to be at the right focus or where the light has a full beam without a hole in the hotspot?
I don't think I have ever seen anyone actually state focus length or how they measured it in a review.
I also don't see why they would include it.
I understand that I could be helpful to determine the minimal distance where you get the correct beam.
Do you mean where the light source has to be to be at the right focus or where the light has a full beam without a hole in the hotspot?
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Marduke
Flashaholic
The focal length is far too small, and beyond the capability of most CPF'ers to measure. It's thousandths of an inch and occurs completely inside the reflector. It's based solely off geometry, not the power source.
Marduke
Flashaholic
I think you have the wrong idea of what the focal length/point is. It's where light in the reflector converges. In flashlights, it's ideally where the bulb or emitter sits and emits lights as a point source. In flashlights, the focal point never even passes beyond the front of the reflector.
kramer5150
Flashaholic
**edit** oops just read his follow up post.
The only lights I have that exhibit a hole in the hot spot are my Cree drop ins. The hole exists up to about 5 inches in front of the lens. Beyond that the beam is clean.
The only lights I have that exhibit a hole in the hot spot are my Cree drop ins. The hole exists up to about 5 inches in front of the lens. Beyond that the beam is clean.
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