DIYbanter - View Single Post - Why aren't many / most LED light bulbs dimmable?

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On Mon, 27 Dec 2010 16:54:10 +0000 (UTC), (Don Klipstein)
wrote:

In , zzzzzz wrote:
On Sun, 26 Dec 2010 23:56:01 +0000 (UTC), (Don
Klipstein) wrote:

In , zzzz wrote:
On Sun, 26 Dec 2010 21:31:57 +0000 (UTC), (Don
Klipstein) wrote:

One more thing: For outdoor or basement nightlighting or security
lighting, I strongly recommend that any white lights (LED or otherwise)
be of cooler color (more bluish, higher color temperature). This is
because night vision is significant in such dimmer lighting environments,
even if colors and sharp outlines are visible. A spectrum richer in
mid-green to mid-blue favors greater illumination in this case.

For indoor, basement, indoor security, and night-lights, I'd think you'd
want more of a red so you don't spoil your night vision. ...or maybe a
white photo-flash and cover *your* eyes, while the no-good gets blinded.
;-)

I've tried all sorts of things for seeing around with little light.
My experience says to make use of night vision. A cool white LED can
illuminate a room to extent that I can walk around and see everything,
using a couple to a few percent as much light as if I used red light.

That's interesting and a bit counterintuitive. I can see fine around the
bedroom, at night, with only the backlight of my XM radio but it's quite
bright. I guess it's not enough to trigger the iris but still make use of the
higher sensitivity wavelengths. OTOH, for astronomical viewing (and
submarines one uses red lights.

Oh yes, I do remember my stretch of time when I was into astronomy.

Red lights were used to see things other than stars, such as star maps,
so as to see in high resolution (from photopic vision) with light that
does not overload and reduce sensitivity of scotopic vision.

I would think the requirements of nightlights are usually different. I
don't see the need to be able to read a newspaper - only to recognize it,
to be able to read the name of the newspaper. There is also the fact
that I don't mind having my night vision attenuated a bit by using a light
that makes use of it for this purpose. I have some green and blue LEDs
that can illuminate a largish living room that well to me with maybe .1
milliamp (and full dark adaptation), though I would only count on low
current performance good enough to do that with .25 milliamp.

I still don't want to lose "night sight" when I stumble from one room into the
next, at night. The light doesn't alter my Braille ability, though. ;-)