Carl, in the previous post, asserted that I was wrong and that reflective paint would do its reflecting as a mirror would, and that the angle of incidence would equal the angle of reflection.
My response:
I recall that lesson from high school physics. And I recall the lesson in college physics that explained that event even better and more subtly*.
That said, that is not how reflective paint works. The paint contains (usually) tiny glass microbeads:
Notice how the light is reflected back along the line it came in on.
That’s why, when you shine a flashlight at reflective stripes on railroad rolling stock, you see a dramatic glow from the reflective paint. The light is being reflected back to its source, with very llttle being dispersed.
The same idea has been used for projector screens. The last one I bought (many years ago) proudly said that it had reflective glass beads in/on it. The idea is that people sit very near the projector. So the light is returned in that direction. That also means the screen will appear very dark from the sides. But who every sits there???
Hence my statement that the reflective paint will return the light towards where it was emitted.
Ed
This conversation reminded me about that “update” in college about the incidence and reflective angles being equal. When we think about that “bouncing” event, we think about it as if a ball was hitting a wall. Or a pool ball hitting the edge of the table. And we all know that the incoming and outgoing angles are the same. And we all know the same holds for light hitting a highly polished metal surface. But where the “basic”
Yep, right after I clicked submit I remembered the product you were talking about. You responded too quickly before I could retract. [:)]
The DA-Lite screen I had in my home theater was not made this way. It was actually gray instead of white. The thinking was that a highly reflective white screen limited your ability to reproduce the blacks in the image.
Gotta remember that the light we’re trying to reflect under benchwork is coming from a variety of direction, if your lights are pointed at your scenery and then bouncing around from there. In a theater setting, the light is projected colinear (at least I think that’s the word my rusty physics is reaching for) – all parallel in one direction.
Very different results and goals in those 2 distinct applications. The special paint will definitely be an advantage in a theater setting, not so much under the layout.
All right let me rephrase: Aluminum foil is not used by the electricial industry as a reflector. I don’t think it passes UL. Lighting manufacturers use Mylar as a reflector in many styles of light fixtures which electricians or their helpers install including styles of lights which are found in every home, like your hall light. Many times it has fi
I have yet to run into a job that contemplates Mylar being applied to walls. Considering that phrase “big $”, perhaps I should find some.
I am surprised that the electrical contractors would take a contract that would include applying Mylar to walls. They are also, then, taking the responsibility if the Mylar application fails. But they got the job, and I didn’t, so they must be doing it the right way.
Since the Mylar is being used in a project for lighting indoor gardens, I wonder if it has reflectivity in more appropriate frequencies than other materials. Interesting.
The “A” in the PAR lamp stands for aluminized as in Parabolic Alumimnized Reflector or PAR lamp.
There must be a reason a mirror finish was preferred for various flood lights, headlights and spotlights.
I remember as a kid using a piece of mirror to reflect sunlight and it sure worked better than a square of white paper…
Now the “properties” of the reflected light as in concentrated or diffused are ultimately what makes for a pleasing atmosphere or a harsh environment.
Lamp manufacturers developed the inside frosted bulb to help diffuse the light for a more pleasing appearance. GE even developed the “Reader” lamp that had additional diffusion.
So what you may want to consider is a combination of highly reflective materials (closer to the light source) to get the light directed to where you want it and softer white materials surrounding the source to diffuse and disperse that light.
This is the sort of reflectivity most likely of use beneath an upper deck and why there’s no real advantage in using a highly reflective material vs white paint. What you’re dealing with is diffuse light in most cases.
I agree Mike, and as you pointed out earlier, the LEDs are very directional so any direct reflective material is not going to have as noticable of an effect. And as I pointed out, anyone with a multi-tiered layout would certainly want to have the underside of the upper deck(s) painted for good appearance anyway. The OP asked which was the best “amplifier” which is what raised the controversy over mirrored surface vs. white paint.
Randy stated it the best:
“The foil, at least as long as it is not all crinkled up, is the better reflector. But the white paint is a better diffuser.”
I had quite a few 48" two-tube fluorescent fixtures mounted in some soffits. The 60hZ hum used to annoy me something awful. After trying several types of electronic ballasts, which still hummed to some degree, I ripped them out and re-wired the fixtures for LED tubes. No ballasts. The 115 hot and neutral wire to each side of the “tombstone” lampholder.
BUT the tubes only direct light about 120° in the direction away from the fixture. I had fixed several reflective devices to try to redirect the light to where I needed it but in the end I wound up having to remount each fixture and turn them 90° to point down.
