Re: Dimmers and auto-iris lenses

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

Ian Shef wrote:

<stuff snipped>

> How about an LED (or even a nightlight) that is within the image.  Its own
> brightness is constant, so an open iris (due to dim lights) makes the LED
> look bright.  A closed down iris (due to bright lights) makes the LED look
> dim.
> Dim LED implies bright room lights.
> Bright LED implies dim room lights.

The winner turned out to be an electroluminescent panel nightlight that I
got for a couple of bucks a while back.  It's got a large plastic border.
At first, it didn't quite give me enough data but when I encased it in
Smarthome "air" shipping bag with big block lettering, three problems got
solved at once.  First, the bag makes the unit waterproof which is rather
important.  Secondly, the lettering disappears as the room lights dim, with
the thickness of the letters acting as a very good indicator of the relative
lighting levels.  As the letters get more backlighting (in relation to
roomlighting) the get more washed out, thinner and hard to read.  When the
room light is out entirely, the lettering vanishes.

It turns out to solve another problem - that of the IR LEDS being too bright
because the camera is designed for a greater range than I am using.  The bag
with the lettering is reflective and reflects enough of the IR LEDs back to
the unit to cause it to drop about an F stop or so.  I'm surprised it
doesn't cause feedback flutter, but it doesn't.  Now I can see detail in the
dog's fur.  Even more interesting is that Hotspot's (the nearly deaf JR
terrier whose in Boodle's crate now as a "test subject") big brown spot
almost disappears entirely when lit only by infrared light.

It's pretty remarkable how the brightness difference in the little night
light draws your eye to that corner of the frame.  Before installing it, you
would be aware that the image was pulsing slightly and that some reflections
were changing when you dimmed the light.  After installing it, when the rest
of the scene is seemingly unchanged, the nightlight is becoming
conspicuously brighter or darker.  Problem solved!

I've also discovered, FWIW, that the IR LEDS in the camera are always on,
but vary in intensity.  I know they go out in bright sunlight, but it's
probably never bright enough in the basement to extinguish them entirely.  I
can always see their reflection now in the bag over the nightlight, no
matter what bulb is dimmed or brightened to.

Thanks again for the idea, Ian.

--
Bobby G.