Re: TRIAC dimmer control spreadsheet; was Re: Controlling Holiday Lights

[sylvan butler <ZsdbUse1+noZs_0611@xxxxxxxxxxxxxxxxxxxxx>]

On Wed, 1 Nov 2006 09:24:03 -0700, Jon Woellhaf <jonwoellhaf@xxxxxxxxxxx> wrote:
> In dimming lights in a home, theater, etc., doesn't the human's non linear
> response to light intensity need to be considered?

As Robert posted, the "practical" way is to just set the light level you
prefer.  It doesn't really matter if the dimmer is passing 80% or 20%,
just so long as you can set it to get what you want.

Mathmatically, it is even more complicated than just human
non-linearities.  Incandescent lamps are also non-linear, and a
mathmatically correct 50% reduction in power will reduce light far more
than 50% in every case I know of.

The whole idea of trying to relate calculated values thru a transducer
to human perception is covered by "perceptual coding."  It is especially
critical in the fields of audio, photo and video digitization and
compression.  No reason to digitize outside the perceivable range, and
when doing lossy compression, to save space you might as well throw away
everything inside that range that doesn't cause a perceptible
difference.

Of course, work in this area was done long before life-like digital
media was even a remote possiblity.  NTSC (and PAL and SECAM) color
television all relied on humans being less sensitive to color than black
and white, so color images needed only to add a little bit of data
compared to B&W.  But even before that, with color photography
perceptual differences simplified the task of reproducing color images.
And so on.

sdb

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