"Icebound" wrote in
:

http://www.hdl-3c.com/customer/mainm...?section=pilot

quote:
The patented HDL-3CT lens technology was designed specifically for the
Aviation Industry.
:unquote

Yet, a search of google archives does not come up with a single instance
of this technology being discussed in any aviation newsgroup.

When I asked my optometrist's dispenser, they claimed never to have
heard of it.

Anybody using this technology? Any comments?

I'm not an expert, but I know a little about optics being a laser
junkie. Anyway, I read the webpage and after weeding throught the
marketing catch phrases here's my two inflation devalued cents:

These are just optical quality neutral density lenses.

By optical quality I mean that they've taken care to get the shape
of the lenses right as opposed to just any old shape. If a lens is
not ground to the right shape it will distort the image. Remember
Hubbles early woes? Most glasses are ground with a simple spherical
surface whereas the ideal shape is often a parabola or asphere.
Spherical lenses are easy to grind, parabolas difficult, and aspheres
downright nasty (usually molded). An asphere is a lens whose surface
follows a complex curve.

Neutral density means it filters all visible wavelengths equally.
Most sunglasses, even grey ones, tend to have a tint. They may
cut the blues more than reds making reds stand out more. My cheapo
$3 swap meet sunglasses do that. In the advertised glasses it
sounds like they've tried to reach that ideal neutral color where
there is no tinting caused by the glasses.

Also, these glasses are nice and dark. By reducing the amount of
light entering the eye in a full daylight view, the dynamic range
is increased. That is, bright objects don't wash out from being
too bright. One analogy would be music that's cranked so loud it's
hard to hear it clearly.

In a nutshell they're new technology probably isn't anything new.
What's special is these lenses may just simply be designed right
and manufactured to tighter specs.

I see on their products pages that they come in various colors,
which is contrary to the neutral density rule. Ideally one doesn't
want color as, of course, it colors what you see.

Ultimately though everyone's eyes and preferences are different
and the only reliable test is for the individual to try them. One
person may think they're a godsend while another may find them
unbearable.

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism

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