Re: Plastic lenses
- From: "J. Clarke" <jclarke.usenet@xxxxxxxxxxxxxxxx>
- Date: Mon, 29 May 2006 13:21:04 -0400
RW+/- wrote:
On Mon, 29 May 2006 05:21:15 -0400, J. Clarke wrote:
RW+/- wrote:
On Sun, 28 May 2006 17:47:28 -0400, J. Clarke wrote:
RW+/- wrote:
On 28 May 2006 15:47:18 -0500, David Dyer-Bennet wrote:
RW+/- <eat@xxxxxxxxxx> writes:
On Sun, 28 May 2006 15:18:52 -0500, Eric Schreiber wrote:
RW+/- wrote:
refractive index is not the same.
Assuming some appropriate material existed, the refractive index
being different wouldn't matter. Don't think of it as a drop-in
replacement for the glass elements in an existing lens design.
Instead, think of it as an alternate material from which new lenses
could be crafted.
Such a material wouldn't have the same refractive index, but it
would have a *known* index, which would be taken into account when
designing lenses, just as the refractive index of glass is now.
If such a thing were feasible it most likely would have been done by
now. The quest for lighter eye glasses has been going of for years.
Yes, and has resulted in essentially all eye-glasses now being made
out of plastic.
Most, far from all.
Another thing that has to be considered is the stability of the
material used.
Yes, that can be an issue -- both strength to resist deformation (and
remain held in position), and also change in size with temperature.
Temperature is one key for sure. Another thing to consider is
resistance to Ozone, and other chemicals. The Sun does an excellent
job of destroying plastics along with natural and/or unnatural
airborne pollutants.
It also does an excellent job of destroying Leica shutters if you
aren't careful about how you set the camera down and are forgetful
about lens
caps. Does it an awful lot faster than it will damage a plastic lens.
Some plastics will hold up for decades in outdoor exposure without any
significant loss of optical performance. Others won't. But camera
lenses generally don't get that much direct sunlight unless you shoot
all day every day at the beach or something.
I have yet to see any plastic hold up for decades under your scenario.
Have you made an intensive study of the environmental durability of the
many plastics on the market or are you just making a casual observation?
Had you applied this critique/question of yours to your original statement
you would never have stated something so foolish.
If you'd like a rather simplistic test for light transmission of
materials try and start a fire with them on a sunny day.
With what? I'm sorry, you've lost me. Never had any problem starting
fires with plastic magnifiers as long as the diameter was sufficient,
if that's what you're suggesting.
You got it, all by yourself, eh? You also seem to understand that there
is a significant difference. Good for you. :)
Huh? Who said anything about "significant difference"? I think now that
I see your problem, you jump to conclusions without adequate research.
Wrong, oh troll under the bridge,
Thank you. I was undecided as to whether you were worth continued effort.
That statement makes the decision easy. You clearly aren't. Thank you for
clarifying that point.
<plonk>
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
.
- References:
- Plastic lenses
- From: Alfred Molon
- Re: Plastic lenses
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- Re: Plastic lenses
- From: Alfred Molon
- Re: Plastic lenses
- From: Eric Schreiber
- Re: Plastic lenses
- From: J. Clarke
- Re: Plastic lenses
- From: J. Clarke
- Plastic lenses
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